> those studying the feasibility of Japan or Germany surviving a long war with the US said the capability of the US for war production would bury both countries <
On some level the German and Japanese leadership probably knew that. But they were hoping for quick, early victories, followed by a favorable negotiated peace.
And that was a reasonable assumption. Most European wars before that time ended that way. Fight for awhile, then gain or lose a few provinces.
(Perhaps Hitler and Tojo should have studied the US Civil War more carefully. That war was the harbinger of things to come.)