It's difficult to impose sanctions without having control of waterways. The US can enforce sanctions against Iran and Russia, but the reverse is not true. This

It's difficult to impose sanctions without having control of waterways. The US can enforce sanctions against Iran and Russia, but the reverse is not true. This puts the former is a position of advantage. True, aircraft carrier diplomacy is a bit more subtle than the the "sign this treaty or we'll blow up your harbor" gunboat diplomacy of old. But it's still the application of force to put the nation at a diplomatic and economic advantage.