There is 0% chance that the US would not respond to eliminate that adversarial pact, with violence if necessary. The US just wrapped up two 20 year wars, one of which had nothing to do with anything.
As someone who lived under Soviet occupation, we never had any doubt which one is the evil empire. Joining NATO is just good sense for countries unlucky enough to be geographically close to Russia. One does not just live next to Mordor.
The issue is for the good of the world, they can't be allowed to join NATO. If the price to pay to avoid WWIII is that Ukraine just doesn't join NATO, that's worth it. It worked for years. Clearly Russia views it as a direct threat, since NATO is really just an extension of the US military.
The price to stop Putin in 2014 would've been a local war with NATO losses. The price to stop him now is to risk walking the nuclear line. The price to stop him in another 10 years will be guaranteed nuclear war.
The price in 2014 was just to not overthrow the democratically elected government in Ukraine, and rewrite the Constitution to change their stance on joining NATO. What is the value in skipping past that part and pretending it doesn't matter?
No, Ukrainians knew why they took it down. Eastern European people are not so easily fooled, we see quite easily through Russian deception and propaganda.