The USA is a staggeringly wealthy country. It can mobilise resources on a scale that no other country can come close to.
It is the largest economy in the world with a per capita GDP that’s typical of much smaller resource dense countries.
As usualy, Trump is just objectively wrong, or lying.
If there are a lot of Americans who are poor, and there’s a great disparity in wealth—that’s because people like Trump have got their hands on nearly all of it. And the only politician close to talking about that issue is Bernie Sanders.