If Putin decided to push for the whole enchilada, what would be the next country that he would invade?
I don't think it will be a NATO country.
If he attacks NATO, he can't be
sure that the war will remain localized, and purely defensive (like Ukraine). For example, he attacks the Baltics - suddenly he can start losing Russian Navy vessels all over the world, Murmansk and Vladivostok can get hit by cruise missiles, the Trans Siberian railway can be taken out, and so forth and so on, with things spiraling out of his (or anyone's) control very quickly. I mean, aside from Biden being a nitwit, why would NATO limit the response geographically to favor Putin? That would be like circling the remains of our navy around Hawaii for the next 4 years after Pearl Harbor.
So . . . taking Poland and the Baltics off the table for now, I'd expect him to turn south towards some of the other former Soviet republics. I don't think people in the West will get too worked up if he invades Berzerkistan or Kablamistan. (Unless they've been paying off Hunter, too.)