Why does the USA gives so much money to Israel every year and gives them weapons? What benefit does Israel give the USA?

Israel (and KSA) serves to destabilise the West Asia, region which is crucial both economically and strategically to petrodollar and to military part of US hegemony. It also served and still serves as proxy war area against USSR and now Russia.

Absolutely worst scenario imaginable for USA would be that area unifying under some kind of Arab entity.