The Thompson submachine gun was a fully automatic piece of work whose extensive use by gangsters during Prohibition, and mobsters subsequently, led to a federal ban on automatic guns about 1936. The law has been in force ever since.
Which you might not know if you watch the Rube Tube. Its supposedly sophisticated commentators often contend that automatic guns are freely available. When corrected they turn (somehow) to the notion that semiautomatic guns are just as bad. Which may be why some of our more dimwitted politicos are out to ban semiautomatic weapons.
Nothing about semiautos, however, equals the firehose effect of a one-trigger-pull full auto. Especially not a Tommy gun, with or without a concealing fiddle case. Rat-a-tat-tat.