As you can see on the message they sent to you, binance has a separate platform for its US-based users which has different terms and whatsoever. Its because of the us regulation/law. FAIK this happen when US authority launches a legal case against BitMEX.

You can read this similar case and article to yours https://www.theblockcrypto.com/post/84020/binance-blocking-us-users-exchange-email-2

And you can reach them to recover your account and send your assets to their us based exchange.