What’s the difference? Over there, only establishment parties are allowed, and a few dissident parties that don’t present any serious threat to the establishment. Putin makes sure that anyone who could be competitive, or make him look bad, is kept off the ballot. Often, he finds an excuse to throw them in jail.
Same way here. In fact, the U.S. has an incarceration rate that’s comparable to Russia’s.
Another thing is, like Russia, the U.S. has a habit of criminally investigating dissident politicians.