Sry but US didn't need to be involved in a war to feed their economy.
The war was alrdy raging in EU and China and all the allies fighting were dependent of US materials. Moreover in 1939 teh US economy had alrdy recovered from the great depression.
http://www.usstuckonstupid.com/sos_charts.php
US were more concerned with the War in the Atlantic and the way to protect their marchand fleet and their neutrality.
The last thing they wanted was a war in the Pacific that proved way more costly than profitable.
http://the.honoluluadvertiser.com/pe...acific/numbers
You'll see easily (bottom page) that despite suffering for nearly no destruction in its continental soil, the War did cost much more to the US than any other nations.
The huge cost of furious destruction all over France is also easy readable.