The tax treaty
None
The United States has no income tax treaty with Brazil. Dividends, interest and royalties from US sources are withheld at the standard 30%. Money you earn for work you do in Brazil isn't US-source income, so nothing is withheld on it.
Stripe
Available locally
Stripe takes businesses registered in Brazil, so you don't need a US company to use it. A US LLC gets you a US Stripe account instead, paid out in dollars to a US bank, which helps when most of your customers are American.
Banking
Mercury available
Mercury opens accounts remotely for US companies whose founders live in Brazil. It asks for the EIN, the formation documents, your passport, a real business address and a description of the company's existing or planned US operations. Relay asks a non-US owner for a US address, an ITIN or Social Security Number and a US operating presence, so it rarely suits a founder living in Brazil.
The time difference
UTC-3
New York is 1 hour behind Brazil in summer. Everything we do is in writing, through your dashboard and email, and we reply within one business day, so the time difference rarely slows anything down.