You can spin up a new entity quite quickly at https://wyobiz.wyo.gov/Business/RegistrationInstr.aspx. The LLC will be a passthrough entity by default, absolving you of US tax, and making any income earned taxable in your current jurisdiction (ZA). Wyoming state tax is 0 if you have no assets in the state (you will not).

You'll need someone with a social security number to help you set up an EIN with the IRS (basically the US version of a tax ID. You can do this yourself if you have a social security number here: https://www.irs.gov/businesses/small-businesses-self-employe..., but given you're international you'll need to use a service like this: https://www.northwestregisteredagent.com/start-a-business/ei... (not an endorsement).

Then you'll want to set up a bank account with a service like Mercury (https://mercury.com), and a merchant account with a processor like Stripe or Braintree.

Obligatory - I am not a lawyer, this is not legal advice.

Happy to chat further if you want to ping me at my bio contact details.