Canadian Politics Today

They had fully automatic weapons in the twenties, and most American men, certainly those who served in WW1, would be familiar with them.

Not in general use. The Tommy gun was invented as a trench weapon for WW1 but was too late to see service. It was a gangster weapon that didn’t see general military use until WW2 and wasn’t that popular. The primary US infantry weapon was the M1 semi automatic with an 8 round magazine. The British Lee Enfield bolt action held 10 and was more accurate.
The M16 which the AR15 is based on didn’t see service till Vietnam Nam.

The NRA types think they can turn the clock back to the fifties, in spite of the population doubling, demographics changing and providing unrestricted access to AR15 style weapons to every whack job in the country. As usual, their solution to too many guns is more guns.