The Soviets were parking nukes in Cuba in striking distance of the White House. If that's not legitimately terrifying to you, I just don't know.
Not anymore than the US being able to strike worldwide to this very moment. They are the only country that has used nuclear bombs against civilians.
The big problem is having one country be able to do it without deterrents and with impunity. MAD is a good thing, if anyone will have those things at all.
Their nukes are still within striking distance.
Which directly followed the USA stationing Jupiter missiles in Turkey with the range to strike Moscow. As part of the mutual climb down from the missile crisis the USA removed the Jupiters, as both sides then understood the wisdom of avoiding hot brinkmanship