Where Should I Register My Online Business?
Businesses with multiple locations can become thorny from a legal and tax point of view. While none of the shipping and manufacturing of your products is being done in the United States, you will be soliciting orders from -- and, presumably, needing a bank account for payments in -- the United States. Therefore, the threshold question becomes whether that activity alone creates enough "contact" with a particular state to require that you register your company there.
What is considered contact? Having a physical office within the state, making regular business trips into the state and repeatedly soliciting for clients within the state (as in a directed advertising campaign), to name a few [b]. It would be wise to speak with an attorney who understands international "jurisdiction" issues. Also speak to your accountant: Just because you don’t have to register as an entity in your state doesn’t mean that you won’t have to pay taxes on income derived from there. Overall, you may find that the simplest, most elegant and most cost-effective solution would be to register in Brazil.