That isn't exactly how Ukraine broke away from the USSR. Ukraine broke away by the USSR dissolving.

So if the US dissolves into, say, Alaska and Hawaii and Puerto Rico and the "other 48", and then Alaska votes to rejoin Russia, then the 48 would be unhappy, sure. But they wouldn't have any say, because in this scenario Alaska wouldn't be part of the US any longer. In the same way, Russia has no (legitimate) say, because Ukraine isn't part of the USSR any longer.

It's kind of like how the UK didn't have any say over the US after that 1776 thing, and when they tried to act like they did, it turned into the War of 1812.