1939 was a long time ago, everyone who made important decisions then is now dead. The world was completely different back then in technology, culture and economy. No country that has been around greater than 20 years has held a consistent foreign policy. While what you said is true, it is completley irrelevant to a discussion of modern US foreign policy - we aren't the isolationists we used to be.
Where we are today is a direct consequence of what happened in the past. The US did not have military posts in Europe or Asia prior to WW2, yet they have been there since.
Further, that is when the US actually secured (that's what we are talking about, right?) peace on two continents (after being asked).
