Not only that, but I imagine any sort of permanent or semi-permanent base of operations in the Gulf of Mexico would have been sitting ducks to defense units on the continent.
Yes, and what would it have really done? Slowed us down and thats about it. Americas industrial capacity far exceeds that of Japan and Germany. Maybe not both combined, but we had England and Russia to help with Germany. And it probably would have left Portland, Seattle, Denver, New Orleans, Pittsburg, and all the other manufacturing cities untouched unless they were getting hammerd by US bombers and planed a one way ride.