this gets into a completely seperate thing. He could not give them it without congress but the US only very reluctantly restricts commerce. Its a very different thing to say im not going to fund your war and im not going to sell you stuff when dealing with a long time ally. And no you don’t just throw away diplomatic relationships easily. If countries did they would have stopped having dealing with us in trumps first term.
It would not have been impossible but it would have been problematic. I mean he could send troops with the war powers act. Its possible but not really something he could realistically do.