Secession happens all the time all over the world, but people in the U.S. are forbidden from even discussing it. From Ryan McMaken at mises.org:
By now, it should be abundantly clear to all that the official US regime narrative on Ukraine is that one is supposed to be in favor of Ukrainian political independence. That is, we’re supposed to support the idea that Ukraine is a separate state that is politically independent from the Russian state. By extension, of course, the idea that Ukraine is a sovereign state also implies it is separate from all other states as well.
But how did Ukraine get that way? States, of course, don’t appear out of nowhere. They generally come into being through one of two ways, or a combination of both. States can be formed out of two or more smaller states through a process of conquest or voluntary union. And states can result when a part of a state secedes to form its own state.