As Brazilian internal crisis raged on, Lincoln Gordon, US ambassador to Brazil, was directly instructed by Lyndon Johnson to do whatever was necessary to support the coup. It's believed CIA had a role supporting pro-democracy street rallies, the files concerning this time are still classified.

When the coup was evident, Johnson sent an aircraft carrier loaded with ammunition, arms and other materials to help on the potential civil war.

It wasn't necessary, tough.

US supported the opposition, but didn't cause the coup. It was essential due to Brazil's own internal dynamics.

If you're interested in more details, you should read Skidmore's The Politics of Military Rule in Brazil, 1964-1985.