russia has over 100k troops in fully operational combat units that are well equipped and trained, and have been planning logistically for a while now. They also have regional combat air superiority i presume. apparently an amphibious force under way, with cruiser/destroyer and sub support too. of course they have a strategic nuke deterrent as well as a hypersonic missile anti naval capabilities, and the ability to deny space and air assets.
the US is not getting in the way of Russia's goals in Ukraine, and if they try anything militarily it will look like the charge of the light brigade.
the navy can't sail assets into the black sea without essentially being a sitting duck.
it would take a significant buildup, that we can't afford, and any real deterrent we have is not credible. we can't afford ww3 or a general first world confrontation, or a nuclear conflict, over Ukraine. Our interests are significant but not critical there.
We lost this battle long ago, so the only choice is not to fight it.