Germany sends a diplomat to Mexico.
"Compadres, have a look at your northern neighbor. They're already fighting a two front war in Europe and the Pacific. A hundred years ago they seized half your country. You could make it a three front war and get that land back. Sieg heil! (coughs)."
The Mexicans listen and smile, then go into a room to talk this over.
First one speaks. "Is he crazy? This is the United States he's talking about. If we go to war with them they'll take away the other half of our country!"
Second one answers. "He's working for Hitler. He really is crazy."
The third Mexican comes from an ethnic minority. "My family used to be German. I like what he's saying."
The other two guys look at him. "Yeahyahyah. Go brew some beer."
And that is the history of Mexico in World War II.