For about 30 minutes.
lol
The US isn’t the entire world. They don’t “need” the US to continue to fight, most of Europe will supply them
We may also know why the people of the Ukraine have a deep seated hatred of any rule from Moscow. Memory of a genocidal famine and Communist misrule will do that. So it's a complex situation. Somebody used to dealing with such is required. And between Biden and Trump the choice is pretty damned clear.