The choices are:
Stop Putin now. Relatively cheap, requires no US military on the ground.
Or,
(The Euro’s foolishly do not have the weapons stockpiles and production capacity to stop Putin.) Let Putin get his warm water shipyards and additional ports, control of vast undeveloped petro resources (it’s not that Russia needs more, it’s the control issue), more bodies for cannon fodder, Ukraine’s steel plants, the threat of nuclear blackmail firmly established...
It’s not that the problems we have now are unimportant, it’s just that they will pale in comparison to the certain problems of a Russian victory. The best outcome would be in a decade or two a Russian dominated if not controlled Europe and a new Cold War costing, what, several trillion $$ per year? I think that’s pretty optimistic, actually. Next best would be an even more costly conventional war that similarly grinds to a standoff, but Western Europe might be saved. Worse of course is if it goes nuclear. In any case, even if the US, Russia, and China end up in an uneasy standoff, the nuclear proliferation in the interim almost certainly blows up in 50 years or so due to some other party. Happy Geiger counting for our descendants.
You are dreaming. After the Ukraine experience there is zero chance Putin attacks Poland or Hungary. Those do not even share common border with Russia.
The only cold war is the gleam in eyes of American Neocons. Putin does not need a cold war, but American Neocons certainly do.