Well, NATO never had the ability to actually stop the Warsaw Pact from making significant initial inroads into even West Germany, except maybe at the tail end of the Cold War era. Deterrence, the threat of nukes, and the ability to make Moscow either get it all fast or inevitably lose (thus making any attempted invasion a very high stakes gamble) were pretty much the cards NATO had to play. Likewise, now, whether or not the Russians could steamroll the Baltics doesn't make that much difference. There's no way to put enough force in there in peacetime, on a regular basis, to stop such a blitzkrieg, but the "soft" factors--international opinion, economic realities, the dismal prospects of an increasingly economically strapped Russia in any protracted conflict with the West--make it fairly unlikely that Putin and Co. would do anything so rash.
Same way they could have probably toppled Kiev if they had really wanted to. The costs would have made the game not worth candle. Ditto for the Baltics I'm guessing.
When you live next to a country the size and power of Russia, unless you're China you basically live with the specter of what they could do to you if they went off the rails. And even China is mostly protected by soft factors too, as again there is little way to stop a land power like Russia from taking a lot of territory fast on its border if it felt like it. Holding it, that's another story, but slim comfort for the poor bastards in the steamroller's way I guess.