And in this case the US participation should come. Wouldn't be better to fight a Putin's Russia that was weakened in Ukraine? Perhaps weakened so much, that Putin's won't attack at all. Perhaps weaken so much, that the US can scale down its European military force deployment (saving money) and concentrate on other things (China).

So yeah, US investments in Ukraine directly benefit America. Ukrainians are fighting for Americans. So much so, that they are destroying Russia's nuclear weapons capabilities (destroying radars, strategic bombers, submarines and ships, weapons arsenal, ballistic rockets, carriers of nuclear weapons like Iskanders).