They can also just legislate you out of existence: "You want to operate here? You comply with the law. And that means a backdoor."
As long as this service is commercial (which apparently it is) it will have a payment gateway, and that point can be easily blocked by a local government.
The US has a lot more influence in these kinds of things than you would think. I'm continually amazed at how easily countries buckle when faced with, for example, financial industry sanctions. Look at the way copyright law has changed over the years.
As long as this service is commercial (which apparently it is) it will have a payment gateway, and that point can be easily blocked by a local government.