Unless the US ceases to conume oil at the rate it does, it will never be able to be isolationist. It has consumed nearly all of its own reserves and *must* import oil or let its economy grind to a halt. The next big need will be water.
Isolationism, as Doc Bungle suggets, is a fantasy.
Since 1801 (when Jefferson sent the US Navy to Tripoli to protect American interests from the Barbary Pirates), the US has been involved in various military actions abroad to protect their interests. This will continue to the case until the US ceases to exist.
The US, while rich in natural resources will always need to go somewhere to import resources (and goods they can't afford to manufacture). Whenever this occurs, there is always the possibility of "friction" with foreign powers.
Check out this link for a complete history of all American battles on foreign soil:
LINK