Tweed wouldn’t have been an option in the US because there was strict rationing of natural fibers for use in military uniforms. Synthetics, especially Rayon, were commonly used.
Also as a result of the shortages, men’s clothing became more austere to conserve fabric, so pocket flaps, pants cuffs and pleats were kept to a minimum and vests disappeared. This austerity became something of a patriotic statement.
The counterpoint to this trend was the advent of the zoot suit in the early 40’s, which was extremely flamboyant in line and color (it was actually considered illicit contraband because it flaunted the wartime restrictions). While this costume wouldn’t have been common among the moderately wealthy, it did influence all men’s fashion by favoring a higher beltline and boxier jacket.
The wide-brimmed fedora was the ubiquitous headwear of the period.