[pcrh]

After WWII, the US was pretty much the only functioning manufacturing nation for a decade. In addition, new markets opened up to US manufacturing due to the dropping of trade barriers with, and competition from, the markets of the British and French Empires as well as Japan. This advantage also lead to faster technological development in the US compared to other markets for a while.

These advantages slowly eroded as other economies were rebuilt. They nevertheless lasted well into the 1970's.

[Amezarak]

While that might have helped the domestic manufacturing market, international trade was not a substantial part of the US economy for a long time - in 1950-1960, imports and exports were 4-5% of GDP (with exports usually just barely north of imports.) They're triple that today. The pre-World War II import/export statistics aren't much different from the post-World War II import/export statistics, but the economy was much different. I don't see how any argument about international trade can apply, based on the data.

After all, it's not just competitors that are gone, it's customers too.