Basically, you’re right. When WW II started, I don’t think the United States was rated in the top ten militaries of the world. People need to remember that during the 30’s, our army trained with broomsticks, yelling bang, and cars drove around with signs of TANK on them, acting as tanks. Years ago, I use to marvel at how all these great military leaders where around at the time we needed them. Found out it was not by accident. George Marshall, during his time in the army, when he would meet someone who impressed him, would write that person’s name in a black book. When WW II hit the fan, he had a ready list of leaders. I have also read and heard that when war comes, the incompetant’s are eventually swept aside or killed.
A similar thing happened during the Civil War. At the beginning, the Union Army was for the most part, a mess. Four years later as the true leaders emerged through the ranks, it was by far the most powerful army the world had ever seen.