Tether is now not usable by American traders. They changed their terms of service to attempt to limit their exposure to US interference. They are attempting to be their own central bank and other exchanges play along because it helps to prop up prices and keep people from leaving the crypto ecosystem. Feed them some tether, push up the prices, let them play with funny money and they keep their coins and money at the big exchanges that use tether instead of wising up when prices drop back down to natural levels and cashing out.

The issue will only truly present itself when many people try to cash out quickly, exchanges themselves sit on their hands with some and fully block others leaving leaving the room, and people don't believe it can happen to them and continue to gamble.