FYI just another post-script to how many tanks may be in private ownership in the US - this is a 2013 article in the WSJ - you need a subscription to post the whole thing but here is an interesting excerpt:
"Weapons buffs may stock semiautomatics in the gun safe. But nothing makes a statement like having an Army tank in the garage. …there are several hundred to 1,000 private tank owners in the U.S. …Brothers Ken and Gene Neal, owners of Bullet Proof Diesel, a truck-parts manufacturer in Mesa, Ariz., once took their 1966 British Chieftain tank into the desert and joyfully backed it over a rusty car. When their insurance agent inquired about their plans for the tank, the Neal brothers emailed back, “We are going to use it to take over the world.” Says Ken Neal, 45: “A tank is cool.”"
https://www.wsj.com/articles/SB10001...02480951570270