Proximity to the United States had three major consequences. One, it was easier to migrate illegally to the United States than from other Latin American countries. This illegal migration was, and is, often abetted by U.S. employers who sought the cheap labor. Secondly, the U.S. military found it easier to intervene against caudillos who were too rambunctious or anti- gringo , or to defend the frontier when it was thought that there was too much illegal immigration. Thirdly, the oil concentrated attention, especially that of the U.S. government.
Mexican oil is today only a small part of world production.
But in the earlier part of the twentieth century, it played a statistically more significant role. To tell that story however one must tell the story of the Mexican Revolution. The Mexican Revolution was the first of the great antisystemic revolutions of the twentieth century. It is usually dated as having occurred in 1910, with the rising of Francisco Madero against Porfirio Diaz. The Mexican revolution had very ambiguous results.