And then, of course, there's the fact that nobody is particularly interested in seeing their capital illuminated by the soft afterglow of a mushroom cloud...

True enough.  But......

There's a continuum of coercive action that one state can take against another that runs from doing nothing to thermonuclear war.

Economic sanctions being the most likely.

A US embargo on Russian oil is a nice toothless measure (because the US imports only a small amount from Russia) that will have tremendous symbolic consequences.

It's when the big boys get into pissing matches that everybody else just gets pissed on.

Even a small, symbolic cut in Russian oil output could have a big impact on prices, because demand is so tight.

And I'll give my consent to any government that does not deny a man a living wage-Billy Bragg