I can't find any source suggesting this was actually a thing in the 30s and 40s. All I can find is the Zimmerman telegram from a hundred years ago which the Mexicans weren't exactly enthusiastic about.
In any case, I doubt there is any realistic threat of a Mexican invasion beyond fantasizing from political fringes.
alt Hacker News
I can't find any source suggesting this was actually a thing in the 30s and 40s. All I can find is the Zimmerman telegram from a hundred years ago which the Mexicans weren't exactly enthusiastic about.
In any case, I doubt there is any realistic threat of a Mexican invasion beyond fantasizing from political fringes.