Try bybit? I think it's better than bitmex as you can use a % on increases so you can stop at 25% profits and set stop losses at 5 or 15%.
The OP is looking for US-friendly exchanges. Bybit prohibits trading from the US, same as Bitmex and Deribit.
How about huobi? Because in a few years ago, I used Huobi before I found bitmex, but I don't know what is happening now. Maybe you can visit on their site on hbg.com because huobi global has been changed now.
Huobi Global gave US traders the boot. They have a US-facing site now (huobi.com) but there is no leverage at all.
You can go to Binance, which is a great exchange and a high leverage. A special thing is that the liquidity is also very high.
Binance doesn't allow US traders to use margin and in fact is kicking them off the site entirely next month.
Looks like there are no Bitmex alternatives for US traders....