I doubt US troops would have ever been committed, and Trump seems to intend to sacrifice as much of Ukraine as he can get away with. But consider that if Russia takes over all of Ukraine after all the "support" we've provided it will damage this country's image, almost as bad as giving Afghanistan back to the Taliban after 20 years did, and presumably the USA's prestige matters to the people whose opinions count even if they disagree with the trend of US policy.
The best that's going to happen is the de facto war will end with Russia keeping what it's stolen, which isn't that bad considering that before WW2 the Crimea and the area roughly coextensive with that we call the Donbass were in the USSR, and the unconquered parts if Ukraine used to be eastern Poland, so in the long run Ukraine still breaks even.
That's a geostrategic defeat, as much as the dissolution of the Warsaw Pact was for the rulers in the Kremlin and the return of the Sinai to Egypt was for "the Zionist entity," but then many people say those areas should never have been conquered in the first place.
It might be unwise to insist Ukraine become part of NATO, but NATO and/or its constituent nation-states should guarantee its independence and its borders, and Ukraine should be included in the European Union if the people of the Ukraine and the constituents of the EU agree. (Note that joining the Eurozone and the Schengen area would still compromise Ukrainian sovereignty to some degree, perhaps even more than joining NATO.)
Objectively speaking the USA needs an enemy, one whose disappearance would not greatly undermine the USA, and that can't be China because most American consumer goods are made there and Chinese interests own big portions of the US economy. Since 1941 this country has been dependent on the idea of a foreign threat to sustain its military-industrial complex, and an isolationist non-imperial USA would soon wind up a third-rate power like Belgium or Thailand. Russia is not the enemy I would choose, but nobody listens to me so Russia would have to do.
Therefore Russia cannot be allowed to conquer all of Ukraine if the USA is to continue as an entity worth considering. That would look like weakness, whatever incidental benefits it provided to some people, and a weak USA will soon find itself under some kind of attack from all the peoples it's damaged in its imperial course. A USA without NATO, without military bases in "friendly countries," without enforceable pretensions to being a Great Power, would be as internationally weak as it was before the Spanish-American War. No foreign power would take it seriously, and even the Monroe Doctrine would be dead in the water.
So it would be extremely unpatriotic for the US government to sell out Ukraine, and anyone who'd do so is a traitor.
