That's irrelevant, their purpose is to act as a deterrent. By invading Russia would also directly attack American, British, German, Canadian etc. soldiers which not something their governments can just ignore. Anyway it's not the 1930's, considering the current political and economical environment there is absolutely no rational reason for Russia to invade the Baltic states (unlike eastern Ukraine or Crimea). What would they gain by doing that, 5 million people none of whom want to be a part of Russia and a shitload more sanctions (assuming if it does not escalate into a full-scale war with the west which is again something Russia has nothing to gain from).