They use airsoft in WWII and later in every other country in the world except Australia. Airsoft is illegal here and while we are trying to get it legalised, I fear it won't be for a while.
If you do plan to go over there, you will have to rent a WWII period airsoft rifle/pistol. Buying them can cost over 1k.
Just don't do any stupid shit with it. Even though its America, they still arrest anyone who carries it openly without a permit.