All depends on if NATO as a whole isn't just a bluff. Are the UK, Germany and France, the three remaining major economies after the US leaves, actually going to go to war with Russia over Lithuania (no offense at all toward Lithuanians), for example? That's what he's testing, and that's why he wants the US out.
I don't think it would matter because if Lithuania is invaded, Estonia, Latvia, Poland and Finland are joining the fight and that's already a huge war in Europe. Sweden seems ready to defend and if Sweden goes it's pretty safe to assume Denmark and Norway are going as well.
Then, if Denmark is fighting, the Netherlands are probably going to help and if the Netherlands are at war so it's Belgium, you see the pattern. So while I don't think Spain would want to defend Lithuania, they would defend France.
Article Five states that an attack on one becomes an attack on all. This wording is very specific, and they wrote it with this wording intentionally, to get people to be willing to agree to join.
It does not require counterattacks or declarations of war, merely that you consider an attack on a member an attack on you.
How do people respond to different sorts of attacks? How can they theoretically respond if they so choose? These are the kinds of games being played in Putin's head.
NATO could crumble and Germany and France would still come to Lithuania's aid, they're an EU member. With NATO gone UK might technically not be on the hook any more but they'd still get into the fray, despite their faults and their insistence that they're not they're still Europeans.
The actually difficult part would be stopping Poland from bee-lining for Moscow, nukes be damned. They don't spend 4.7% of GDP because they plan on sitting back.
That's a lot of faith to have in treaties. Historically Nations tear up treaties of the drop of a hat. They're only as valuable as the vested interest of those involved.
We have common elections, we have a common citizenship, we have a common identity, in many areas it's even common to identify as European over the nation state. That is, regional identity first, then European, then whatever nation state the region ended up in.
None of which has been tested. It's very easy to claim all that in times of peacetime. When it comes time to go fight for someone else is when the real rubber hits the pavement.
So are those the good guys or bad guys? I don't know anymore. It would be funny America trying to take over a bunch of countries and China coming to European aid. What a screwed up world we live in.