Not to nitpick, but "assault rifle" is a technical term for a select-fire (fully automatic) weapon that fires an underpowered rifle caliber, and any select-fire weapon is quite illegal for individuals to own in the US.

"Assault weapon" is a made up term used to try to discriminate these civilian rifles on the basis of the cosmetic features that make them seem frightening to non-gun-owners. When we talk about a semi-automatic civilian "AK-47" like this, it's really just called a rifle.