The US might want to be careful here. The Mexicans had the Mondragon rifle while the US Army had the M1903 Springfield.
http://en.wikipedia.org/wiki/Mondragón_rifle
http://en.wikipedia.org/wiki/Mondragón_rifle
I think a timeline called the American World War involved a 2nd Mexican-American war in the 1920s. I think that timeline is dead though.
Was there a communist movement in Mexico in the 20s? Here's how it could go. We get the war to happen in 1916, so the US doesn't interfere in WW1. Russian revolution still happens, of course. Would Germany or the allies win without US intervention? I think Germany would, but perhaps someone could educate me on why the Allies might win. The reason I think the Germans would win is because they could get a ton of troops that were on the Eastern Front to the Western Front. Then, the Mexicans have a communist revolution because of the obvious economic instability, which is of course supported by the Soviets. Then it goes on from there.If it's in the 20s, I could see Mexico eventually falls to either communism or fascism.
The US might want to be careful here. The Mexicans had the Mondragon rifle while the US Army had the M1903 Springfield.
http://en.wikipedia.org/wiki/Mondrag%C3%B3n_rifle