Polymarket does. In the US they are a registered CFTC exchange for trading event contracts. That gives them some degree of protection from state actors. It also increases the odds that if you make money you'll actually be able to withdraw it unlike many of these markets. They also operate in actual dollars not make up crypto tokens.

Note that Polymarket's non-US business is crypto blockchain whatever so ... good luck with that. The ability to get your money out could disappear at any time and as far as I know there's no recourse if they just decide to screw you over. Not that CFTC is super effective but it is something.

Ah, makes sense. I've never bothered looking into using either so I wasn't aware of that.

They do: polymarket.us

They do nothing to block US people from signing up to polymarket.com, the block is a farce