[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.