The Americans have no concept of lane discipline.
There’s a couple of differences here, though.
First, the ‘first’ lane on a three-lane highway is often an entry / exit lane; you simply cannot drive in it, or you’ll end up being filtered off somewhere else unless you hop lanes every few hundred yards.
Second, there’s no concept of an overtaking lane like there is here. You’re expected to use whatever’s here.
Isn’t undertaking legal in the US though, so lane discipline is less of an issue?
Well, yes, but you seem to be implying that it’s not legal over here, which isn’t the case. Undertaking isn’t illegal, though driving without due care / dangerous driving is. If you’re swinging in and out of lanes carving people up, that’s what you’ll be charged with; you’re explicitly allowed to pass on the left to overtake slower-moving traffic.