As part of the research I'm doing for the Anzac book (which I'm thinking of renaming to better reflect the geographical area covered), I'm reading a LOT on Logistics. One very interesting book I'm about halfway through at the moment is "The Big L: American Logisitics in World War II" edited by Alan Gropman.
https://www.ibiblio.org/hyperwar/USA/BigL/BigL-Fwd.html It raises several extremely interesting points on why the US was able to supply the allies with so much material. Essentially, it's in large part due to the depression and the massive amount of unused manpower and factories just sitting around idle, as well and the (relatively) very long lead time before the US entered the war.
The US really had several years of lead time before entering as an actual combatant, with the Lend Lease system effectively putting them economically on a war footing well beforehand. However, even with several years of lead time, it wasn't until 1943-44 that many of the production issues were finally sorted out - 1939-42 were absolute chaos logistically speaking.
How does this relate to T2K? Well with the Twilight War the US was not coming out of a decade + long depression which means there wasn't all that spare industrial and manpower capacity just sitting around idle. The US also doesn't get several years warning to build up before entering into hostilities - they get weeks, at best.
Another interesting point is the depression prevented many ideas and inventions being
developed during the 1930's. This, in part, explains the huge leap forward in technology during the war years - development of radar for example. Yes, there were many breakthroughs during the war period, but quite a number of them would have occurred earlier but for the depression putting the dampeners on innovation, experimentation and exploitation. People were still coming up with ideas during the 30's, they just weren't acted upon.
Additionally, the US was not under direct attack in WWII. It's industries, population and research facilities were not being damaged, people killed and so forth.
In T2K it's a different matter - no lead time to war, and (depending on which timeline you're using, 1st ed of 2.x) devastating attacks on mainland US within a year, which, if WWII is anything to go by, is well before production has properly switched to war footing.
There's a LOT more in the book than I've touched on in my rambling above, and well worth checking out if you've got the time. I've come away with a strong feeling that ALL combatants wouldn't have been able to make very many technical advances before the nukes flew, and industry would barely have begun switching over to wartime production. Really drives home the scarcity of the more advanced munitions and the like in T2K...