Your heart is in the right place, but you are incorrect. The made up political term in the US is "assault weapon", created when the "Assault Weapons Ban of 1994" was enacted into law.
"Assault Rifle" is very much an actual term for an actual classification of military firearm, and is a literal translation of the German term to English from the original assault rifle, the Sturmgewehr 44 created by the Germans during WW2. Moreover, the reason an MP5 is called an MP5, is that the MP stands for Maschinenpistole which literally translates to "machine pistol", and is the next closest type of weapon in German parlance to an assault rifle. In fact, the StG 44 derived from the MP44, which fired a smaller cartridge.
Mechanically, both assault rifles and machine pistols operate similarly, the primary difference is the cartridge. Assault rifles fire intermediate rifle cartridges (smaller than a battle rifle cartridge) [e.g. 5.56 NATO (.223 Remington)], and machine pistols fire pistol cartridges [e.g. 9MM NATO]. Machine pistols in the US are classified as sub-machine guns. The history of that is equally interesting, but irrelevant to this sub-thread.
There are no civilian owned Assault Rifles manufactured after 1986 in the US, except when held by a Class 3 FFL (federally licenses firearms dealer), or purchased by a police department or specially licenses corporate security organizations (think PMCs). They are considered to be exclusively military weapons that do not pass the "sporting purpose" test enacted in the Firearm Owner's Protection Act of 1986 (ironically named, since it didn't do anything of the sort). This is especially ironic because the entire reason shortened barrel shotguns being illegal in the National Firearms Act of 1934 was upheld in the US Supreme Court (Miller v United States) is due to it not having a military purpose, the purpose of the 2nd Amendment being that US citizens have an innate right to possess, train with, and utilize military equivalent arms. So taken together, in the US a firearm must have a "sporting purpose" and also be military equivalent in order to be legal... luckily that contradiction does not completely eliminate most firearms.