Dell USA, AFAIK, accepts only dollars.  Dell Brazil accepts only reals.  If you want to pay them with some other currency, you must find a way to convert them to USD or BRL, respectively, and send those to the companies.

I have used my Brazilian credit card, whose bills I pay with BRL, to pay for hotels and other stuff in the US, Europe, Japan, etc; but it was always the credict card company that exchanged my BRL for USD, EUR, JPY and deposited these to the merchants' bank accounts.  Those merchants definitely did not "accept BRL", anymore than Dell "accepts bitcoin".