The USA is today a threat to the entire world, not just for Russia.
Acts of aggression coming from this adolescent though active country follow one another every 2-3 years (after the collapse of the USSR, US destroyed Yugoslavia, then Iraq, then Libya; Syria could be the next if not Russia's direct interference), US is bombing as it's breathing.
The US nuclear threat is real and tangible for Russia because the United States of America is the only country on this planet which has used nuclear weapon.
Moreover, it has used nuclear weapon against a defeated defenceless country - Japan.
This has been done on purpose to show USSR who's the tough guy and to rehearse nuclear attack on USSR's cities.
There is no doubt about that.
There was even a plan how to do it, I guess «Dropshot» was not the first one.
Only USSR's making an equal bomb, which established the balance, saved the world from America's brutal nuclear dictate.