In Tennessee where I live, you must not impede the flow of traffic. If everyone else is doing 80, 85, etc MPH, and you merge over into the left lane to pass, but you go 70? You are breaking the law if there are drivers behind you still going that higher speed and they have to slow down or hit their brakes because of you.
Additionally, if you do not move to the right as soon as you are able to, they are supposed to audibly signal to you (honk) to move over, and if you don’t, they are permitted to pass on the right.
The flow of traffic thing applies to the right lane too, just doesn’t come up as often.