The point remains - what are you accusing the US Navy of planning to do along your coast, and what is the Russian navy supposedly doing to prevent it (and why do you assume they have any better motives than the US does)?

The US Navy deactivated the south atlantic fleet decades ago, and then it announced its reactivation shortly after our official announcement of finding lots of oil... Why should we not be suspicious?

And Russia is here because our government invited them, after US announcement, officially it is for "training", but Russian ships can keep US ships away from the oil rigs (ie: when a US ship is in a place the government here disapproves, the government invites Russian ships to do a "training drill" nearby, and push away the US ship, that will retreat to avoid conflict, a sort of psychological dance).

Mind you, US already used its navy to topple our government before (in 1964 it sent a carrier group to support CIA during our military coup), and US was suspected here of having too much interest in our oil company, this later was proved by Snowden (NSA did lots of spying on Petrobras, including of stuff that is more commercial than strategic), so excuse me if we don't trust US, the past behaviour of US toward us here has not been good (while we have nothing but praise for Russia... yes, I know all Russian issues worldwide, but locally to US Russia always had been a great true ally).