The US might not have been a material threat weapons-wise in 1939 but from about 1938 on the US was spending massively to improve their military facilities and manufacturing capacity in that area. When it came time to make huge quantities of "stuff" the capacity was there.
One must remember that the US did not plan on being in the war prior to mid-1942 at the earliest even after it started in Europe. The peak production point was not to be reached until 1945.
So, if war in any of these scenarios is inevidable with the US for Germany, the longer the delay, the more massive the beating Germany takes.