https://www.rt.com/russia/553074-state-department-americans-leave-immediately/
The U.S. State dept claims it is because Americans are being "singled out and detained" by Russian officials yet the only American to be arrested was a basketball player for possession of marijuana vaping oil.
Because they want to escalate. They will escalate very soon, so buy your supplies.
They gave short notice in Afghanistan, but Russia won't bum rush Ukraine either way, so the Biden regime is planning on escalating, probably with a false flag.