Will Elon Musk be able to cut $2 trillion from US government spending?

Absolutely.

Just have to cut social support, teachers, Healthcare, safety regulations, infrastructure... anything that doesn't make the government money.

And even better, falling GDP causes unemployment to rise, driving down wages as people strive for enough to exist, pushing down inflation. Business makes more money with less regulations, lower wages, and can keep putting prices up above inflation changes. Every rich person wins =)

He'll only try if he can personally take all the money