I did this before I became a citizen and before I had residency. Trust me: You only have one minor problem right now and it's not having a merchant account. Focus on solving that. Setting up a US corporation is a world of expense, complexity and hurt you don't need. The issue goes beyond the obvious, for example it's likely you'll be refused entry to the USA on a tourist visa if you're a shareholder and director of your own USA C corp. [No it's not documented anywhere so don't bother Googling]
If you use Stripe, you dont need a merchant account, only an EIN. Only problem then is having a bank account to transfer the money into. This can often be done in person on a short trip to the US. Be sure to find out exactly what you need in advance - when I set up my bank account BofA told me I needed a form from city hall, which wasn't available on Fridays.
None of my non-US clients has ever been denied entry into the US on any visa because they were a shareholder or director of a US corporation. If anything, they have generally received visas faster than they did before becoming US investors.
Denying entry to foreign investors would actively discourage foreign investment in US industry, which is completely at odds with most of tax code. Indeed, US law is too generous to foreigners who own businesses in the US.
There are foreign investors or directors and then there are one man corporations with no employees, zero capital and where the only shareholder is a non-resident.
