Yet it's still a thing, and a thing we have to take seriously. We wouldn't tolerate Russia getting seriously involved with Canada or Mexico. Don't think they'd tolerate the same with us and the Ukraine. We have to look at strategic implications of such a decision. Would the benefits outweigh the risks? Maybe, I really don't know, but there is a big difference between stiff-arming Russia and moving into their AO.
Yet we've never bothered Canada or Mexico for being involved with Cuba. They're sovereign countries and unless we're going to be as bad as Russia we need to trust them to make their own decisions and we need to respect their sovereignty as we expect them to respect ours.