A perfect union: What's more American than homemade ice cream and root beer?
A fun idea that doesn't require a machine is "kick the can" ice cream, where the ice cream is churned by rolling around on the ground. You can buy a round, sturdy soccer-ball replica in some camping/sporting goods stores. It has an inner canister for the creamy mixture, surrounded by a compartment for the ice and salt. Ref. Source 6