Nobody is hinting that Russia’s mere existence is a threat. Russias perpetual imperialist designs on its neighbors is the threat. Again, the world isn’t watching US-Canadian relations with concern. Nobody in Belgium fears a German invasion despite their equally recent bad history.
Asking if another repressive communist regime was “in its right” to point missiles at the US is outside the question. The United States could easily turn Cuba into a parking lot and yet nobody fears that actually happening. Russia, on the other hand, is a perpetual bully. What did Georgia and Ukraine do to offend benevolent comrade Putin?
Russia abandoned its empire in 1991. NATO enlargement to its borders started in 1997, after NATO destroyed Yugoslavia.
Russia has only started to object in 2007 when the inclusion of its immediate neighbors started.