US banks or financial institutions interested in granting a
mortgage-loan for the purchase of a property in Rio de Janeiro, by a
US Resident working for a US Company in Brazil, with US based salary
paid in a US Bank

This might be tough.

A lender might have difficulty in realising his security in the event
of default. This could be overcome if you could also offer some
US-based security.

But why not raise the finance in Brazil? The Golden Rule is to borrow
in weak currencies but lend in hard.