“Thompson 45 is an assault rifle”
If you mean the Thompson submachine gun, I disagree. It fires a cartridge originally designed for a pistol while an assault rifle fires a cartridge designed for a rifle—unless “gun-control” definitions are used in which case all bets are off as to what is really what.
Technically you are right by virtue it uses a 45ACP, but that would be the same as saying any assault rifle using a pistol round cannot be called thus like the Uzi or an MP40.