[letstryagain]

I think you can own a howitzer in the USA if you want

[jschwartzi]

I think that's because it's really hard to rob a bank with a howitzer.

[rtkwe]

You can own basically anything given enough forms and legal wrangling.

[fludlight]

Two or three of the tanks in the Littlefield auction had functional main guns. You needed a special ATF license for "destructive devices"(?) to take delivery. Getting said license is probably non-trivial, but very much possible for law abiding citizens.