The US can veto the Security Council because the power is there in that smaller scenario. They can’t override the entire UN General Assembly, though. That said, I’m sure there would be behind the scenes pressure from the US on allies voting in the GA.

I’m more concerned about the double standard of the White House skirting Congress to supply Israel with tank ammo (does Hamas even have equipment they’d use that against, you know, besides hospitals and schools,?) vs. allowing Republicans in Congress to delay/prevent aid to Ukraine and possibly hand it to Russia.