The EU can't let Russia "win" as it would set a precedent. If the US withdraws their support, the EU will have no choice but to ramp up theirs, meaning funneling money to the military complex. Double or triple that if Trump goes through with his NATO defunding/withdrawl threats. This could easily destabilize the EU economy, cause internal friction, provide fertile ground for nationalism and, ultimately, lead to the fracture of the EU. Now recall Trump's cordial alignment with Putin, which will undoubtedly encourage this sort of development, and it all starts to look outright scary.
If Germany had any strategic autonomy left (which they don’t, they’re just a US vassal through and through) they would do a second Rapallo, maybe this time also involving China, at that point they’d still have a chance to put their economy back on track.
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This is not about what Russia is doing. Russia, like the US, is an imperial power that cares little about the rights of other. This is about the US testing how much it can get away with by enroaching on what it mistakenly thought was a much weaker Russia than it turned out. And Ukranians are paying the price in blood, often against their will.
However the world let the annexation of Crimea slide in 2014 and that emboldened Russia. Let them chop off a piece of Ukraine now and that will embolden them even more. After all Finland was a province of the Russian Empire before the revolution of 1917 and parts of Poland were under Soviet's control prior to 1941. And that's without going back into middle ages. Lots of places to take back.
In fact, it won't even really be the voting citizens of the USA who make any decisions, because when red/blue splits 50/50 it isn't "tyranny of the majority" anymore, it's tyranny of luck.
Re: your taxes - it'd be prudent to look beyond short-term effects and consider what different scenarios would lead to in the long-term. The EU had no choice but to help Ukraine to resist. Consider where things would've been now if they didn't.