Define "banned".
There's a broad range of phenomena here.
A few places have absolute prohibitions of civilian ownership of any firearm.
Most places place heavy restrictions and obstacles to civilian ownership of firearms, so as to be de-facto bans.
(ie: after deep scrutiny, a civilian might be granted the privilege of owning a double barrel bird gun or bolt action .22 which must be kept in a 1000lb safe behind a burglar alarm, and subject to police inspection at any time without notice)
A small handful of places beyond that improve a bit; there's still obstructions and paperwork, but once you get beyond that, you've got a wide array of choices and contexts in which you can be armed.
A very small number of places within the US have something approaching the full glory of the 2nd ammendment.