I think it depends very much on how interested they are in foreign affairs, and their particular political views.
I don't really fit "Democrat" or "Republican", but I definitely tend to lean more to the "Republican" side on this topic. Trump's platform included trying to get NATO members to "pay their fair share." Like most everything Trump says, that's unnecessarily confrontational, but the point is valid - Europe has been reliant upon US defense spending for decades. Because they know the US is there, they've cut defense spending. As you pointed out, that means they are currently incapable of effectively defending themselves without US intervention.
> It's about Russia being run as an authoritarian imperialistic etno state.
I think you're likely exactly correct here. More importantly, even if your analysis of Russia's motivations aren't quite right, you're "close enough." Their actions are consistent with this view.
> Everytime the US appeases, Russia is encouraged to do more violence, more aggression.
Because Russia currently sees the US as "Europe's military", you're absolutely correct.
> The more clarity the US gives on when and how it will enter war, the less likely it is for the war to take place. And we really just need you guys to have the discpline for the next few years, and then we won't ever need US soldiers patrolling our borders, which seems fair and important (because there are more threats in this world than just the Russians!)
Unfortunately, that's just not how the US political system works. We almost always have a fairly drastic change in leadership (and therefore foreign policy) every eight years. We often have it happen every four years.
There is a reason that Russia occupied Crimea in 2014, then didn't move on to annex more (or all) of Ukraine until 2022: the US had a leader that was unpredictable and relatively aggressive from 2016-2020. With Biden replacing Trump, Putin began spooling up the Russian war machine for the attempt. He'll take what he can take right now, then pause. He'll give Americans time for Ukraine to fade from the popular consciousness before our next election cycle. If Biden is re-elected, I expect he'll almost immediately move to take more territory. If it's someone else, he'll likely wait a few months to observer their policy decisions and decide whether to move or not in ~late 2025 and act in ~mid 2026.
Basically, Europe should plan on the US remaining passive until 2025 at the earliest. The only time you may have is while Putin is integrating Ukraine into Russia (or the "Russian sphere of influence", á'la Belarus). If I were the leader of a European power, I'd be putting defense at the highest possible priority short of a war footing. If I were the leader of an ex-Soviet state, I would be looking to build strong relationships with European states with stronger economies and militaries.
The 2020s are going to be rough for Europe.