Russians would likely shoot at US forces in Ukraine. Then what? I sympathize with the Ukrainian people but Ukraine is not a US treaty ally.
If you're brave enough, the Ukrainian military is accepting volunteers. Other foreigners have already enlisted. Go join them. And I'm not being snarky: if you really believe in the cause then I sincerely think you should do something about it.
The United States is capable of getting involved even if Ukraine is not a treaty ally. I am stating a geopolitical policy preference. Yes, that involves some US soldiers dying.
It doesn't just involve US soldiers dying, it probably means some cities turned to cinders.
There's a line you cannot cross, and wasn't crossed in the entire cold war as bitter as things got-- and that is NATO troops on Russian soil or vice versa.
If you're brave enough, the Ukrainian military is accepting volunteers. Other foreigners have already enlisted. Go join them. And I'm not being snarky: if you really believe in the cause then I sincerely think you should do something about it.