"Isolationism" is a misnomer. It should be correctly spoken of as "Non-interventionism".
As I've said before, "isolationism" as it is used in what passes for intelligent political discourse in this country, is a perjorative, propagandistic term that is almost universally misused. Those of us who believe that a global empire based on hegemonic, naked aggression is bad for this country are in no way suggesting that we cut all ties with nations. Of course we need to continue diplomatic and trade relations with other countries, but interventionism into their internal affairs and their disputes with other countries not only is morally wrong, but it is against our national interests. One, it puts our citizens in danger of terrorist attacks from those who quite understandably and predictably will react against being bullied; two, it needlessly causes death and injury to our troops who have no business being deployed in wars of aggression; and three, because it is bankrupting our country economically.
As Major General Smedley Butler clearly shows in his famous essay, "War is a Racket" (which I suggest you read, it is available for free online) interventionism only benefits small, parasitic, welfare-gobbling elites at the expense of the American people and the peoples of other nations who these policies victimize. Our Founding Fathers recognized this. Pity that rank-and-file members of the Tea Party are inconsistent in their professed admiration for these gentlemen.