While US commitment to NATO is uncertain, the rest of NATO still seems certain. Russia might be able to take the Baltic and/or Poland - but they won't be able to keep it. Soon as they cross the border (or more likely start building up) the rest of Europe will start building up their army to attack back.
A country attacks another one only if it doesn't have political control of it feels that never will. For example Russia doesn't have to attack Belarus and won't have to attack Hungary, and probably not Slovakia. They'll be part of the next Warsaw Pact without any bullet flying if their leaders will get guarantees that they can be leaders forever. Poland looked like it was going that way before the current administration. Ukraine itself have been pro Russia or pro NATO at different times in the last 25 years. No need to attack it when it was pro Russia. So let's see who that "rest of Europe" will be if and when there will be the need to defend some country in the East.
