Its very hard and frustrating because EU doesn't have the infrastructure to introduce/rotate products from country to country. It would be cool to have a shelf only with EU products in every Hyper/Super Market. Send cheese and champagne from France to Sweden one month, then rotate it to Poland. Poland send products to Spain or Romania, and so on. This way the supplier doesn't have to increase production capacity to unrealistic levels, and they get some data on what people from different countries like.
Your economy will suffer no matter what, world is shifting away from US. Best thing to do is take care of yourselves and survive the economic storm that's coming. After that, lead the way to normalize relations with former allies.
I have a database of over 500 brands, it would be very hard to post them all here. The absolute best way to boycott US is to create a Android / iOS app which you can use to scan product logos/packaging while shopping.
US Owned Products (Common in EU)
Brand : Cargill
Ownership : Cargill family
HQ : Iowa, US ___________________________________________________________________________ Brand : Colgate-Palmolive
Ownership : Colgate-Palmolive
HQ : New York, US ___________________________________________________________________________ Brand : Crisco
Ownership : B&G Foods
HQ : New Jersey, US ___________________________________________________________________________ Brand : Sprite
Ownership : Coca-Cola Company
HQ : Georgia, US ___________________________________________________________________________ Brand : Papa John's
Ownership : Papa Johns
HQ : Kentucky, US ___________________________________________________________________________ Brand : Cheetos
Ownership : PepsiCo (via Frito-Lay)
HQ : Texas, US ___________________________________________________________________________ Brand : Vitamin Water
Ownership : Coca-Cola Company
HQ : Georgia, US ___________________________________________________________________________ Brand : Spam
Ownership : Hormel Foods Corporation
HQ : Minnesota, US ___________________________________________________________________________ Brand : Froot Loops
Ownership : WK Kellogg Co.
HQ : Michigan, US ___________________________________________________________________________ Brand : Hubba Bubba
Ownership : Mars Inc. (via Wrigley)
HQ : Illinois, US ___________________________________________________________________________ Brand : Orbit
Ownership : Mars Inc. (via Wrigley)
HQ : Illinois, US ___________________________________________________________________________ Brand : 7UP
Ownership : Keurig Dr Pepper
HQ : Texas, US ___________________________________________________________________________ Brand : TUC
Ownership : Mondelez International
HQ : Illinois, US ___________________________________________________________________________ Brand : Tostitos
Ownership : PepsiCo (via Frito-Lay)
HQ : New York, Texas ___________________________________________________________________________ Brand : Rockstar Energy Drink
Ownership : PepsiCo
HQ : Texas, US ___________________________________________________________________________ Brand : Cookie Crisp
Ownership : General Mills
HQ : Minnesota, US ___________________________________________________________________________ Brand : Pizza Hut
Ownership : Yum! Brands
HQ : Texas, US ___________________________________________________________________________ Brand : Schweppes
Ownership : Coca-Cola Company
HQ : Georgia, US ___________________________________________________________________________ Brand : Chobani
Ownership : Chobani
HQ : New York, US ___________________________________________________________________________ Brand : Jack Daniel's
Ownership : Brown–Forman Corporation
HQ : Tennessee, US ___________________________________________________________________________ Brand : Bel-Vita
Ownership : Mondelez International
HQ : Illinois, US ___________________________________________________________________________ Brand : Domino's Pizza
Ownership : Domino's Pizza
HQ : Michigan, US ___________________________________________________________________________ Brand : Tyson Foods
Ownership : Tyson Foods
HQ : Arkansas, US ___________________________________________________________________________ Brand : Campbell's
Ownership : Campbell's
HQ : New Jersey, US ___________________________________________________________________________ Brand : Milka
Ownership : Mondelez International
HQ : Illinois, US ___________________________________________________________________________ Brand : Barni
Ownership : Mondelez International
HQ : Illinois, US ___________________________________________________________________________ Brand : Ritz Crackers
Ownership : Mondelez International
HQ : Illinois, US ___________________________________________________________________________ Brand : Toblerone
Ownership : Mondelez International
HQ : Illinois, US ___________________________________________________________________________ Brand : Oreo
Ownership : Mondelez International
HQ : Illinois, US ___________________________________________________________________________ Brand : Nature Valley
Ownership : General Mills
HQ : Minnesota, US ___________________________________________________________________________ Brand : Kraft Heinz
Ownership : Berkshire Hathaway
HQ : Pennsylvania, US ___________________________________________________________________________ Brand : Mondelez International
Ownership : Mondelez International
HQ : Illinois, US ___________________________________________________________________________ Brand : General Mills
Ownership : General Mills
HQ : Minnesota, US ___________________________________________________________________________ Brand : Betty Crocker
Ownership : General Mills
HQ : Minnesota, US ___________________________________________________________________________ Brand : Cheerios
Ownership : General Mills
HQ : Minnesota, US ___________________________________________________________________________ Brand : Kraft
Ownership : Kraft Heinz
HQ : Illinois, US ___________________________________________________________________________ Brand : Heinz
Ownership : Kraft Heinz
HQ : Pennsylvania, US ___________________________________________________________________________ Brand : Quaker Oats Company
Ownership : PepsiCo
HQ : Illinois, US ___________________________________________________________________________ Brand : Twix
Ownership : Mars Inc.
HQ : Virginia, US ___________________________________________________________________________ Brand : Milky Way
Ownership : Mars Inc.
HQ : Virginia, US ___________________________________________________________________________ Brand : Skittles
Ownership : Mars Inc. (via Wrigley)
HQ : Illinois, US ___________________________________________________________________________ Brand : Mars
Ownership : Mars Inc.
HQ : Virginia, US ___________________________________________________________________________ Brand : M&M
Ownership : Mars Inc.
HQ : Virginia, US ___________________________________________________________________________ Brand : Juicy Fruit
Ownership : Wrigley
HQ : Illinois, US ___________________________________________________________________________ Brand : Extra
Ownership : Wrigley
HQ : Illinois, US ___________________________________________________________________________ Brand : Bounty
Ownership : Mars Inc.
HQ : Virginia, US ___________________________________________________________________________ Brand : Snickers
Ownership : Mars Inc.
HQ : Virginia, US ___________________________________________________________________________ Brand : Doritos
Ownership : PepsiCo (via Frito-Lay)
HQ : New York, US ___________________________________________________________________________ Brand : Gatorade
Ownership : PepsiCo
HQ : New York, US ___________________________________________________________________________ Brand : Mountain Dew
Ownership : PepsiCo
HQ : New York, US ___________________________________________________________________________ Brand : Sprite
Ownership : Coca-Cola Company
HQ : Georgia, US ___________________________________________________________________________ Brand : Fanta
Ownership : Coca-Cola Company
HQ : Georgia, US ___________________________________________________________________________ Brand : Monster Energy
Ownership : Monster Beverage Corporation
HQ : California, US ___________________________________________________________________________ Brand : Coca-Cola
Ownership : Coca-Cola Company
HQ : Georgia, US ___________________________________________________________________________ Brand : Pepsi
Ownership : PepsiCo
HQ : New York, US ___________________________________________________________________________ Brand : Starbucks
Ownership : Starbucks
HQ : Washington, US ___________________________________________________________________________ Brand : Jack in the Box
Ownership : Jack in the Box
HQ : California, US ___________________________________________________________________________ Brand : Carl's Jr.
Ownership : CKE Restaurants
HQ : Tennessee, US ___________________________________________________________________________ Brand : Taco Bell
Ownership : Yum! Brands
HQ : California, US ___________________________________________________________________________ Brand : Dunkin' Donuts
Ownership : Inspire Brands
HQ : Geordia, US ___________________________________________________________________________ Brand : Pringles
Ownership : Mars Inc. (via Kellanova)
HQ : Virginia, US ___________________________________________________________________________ Brand : Chick-fil-A
Ownership : Cathy family
HQ : Georgia, US ___________________________________________________________________________ Brand : KFC
Ownership : Yum! Brands
HQ : Texas, US ___________________________________________________________________________ Brand : Wendy's
Ownership : The Wendy's Company
HQ : Ohio, US ___________________________________________________________________________ Brand : Five Guys
Ownership : Murrell family
HQ : Virginia, US ___________________________________________________________________________ Brand : Subway
Ownership : Roark Capital Group
HQ : Connecticut, US ___________________________________________________________________________ Brand : McDonald's
Ownership : McDonald's
HQ : Illinois, US ___________________________________________________________________________ Brand : Lay's
Ownership : PepsiCo
HQ : New York, US