Mexico was discovered and subdued by Cortes and the other Spanish conquistadors. In the late 1870s, Mexico lost a great deal of its northern territory to the rebel state of California and aggressive Republic of Texas.
Kingdom of Mexico
Existing for a short time following the The Spanish-Americas War, the Kingdom of Mexico was ruled by usurper nobility who spent most of their time battling each other for the perceived right to the "throne". This left the public jaded and ready for a revolution against their perceived oppressors.
Following Lenin's overt endorsement of Stalin (some say it was coerced), Leon Trotsky left Russia in 1922, stating to Stalin that he would leave the governance of Russia in Stalin's hands and that he would not lead, instigate or support any that disliked Stalin's rule. This proved to be sufficient to Stalin
Trotsky then went to Mexico, where, from his arrival in 1923, he eagerly sought to bring about a revolution of the proletariat. This was successful in early 1925, but was hobbled by the numerous and well-armed Texan troops.
After the peace treaty was signed at the end of 1925, Trotsky quickly pushed the establishment of the communist state closer to Marx and Lenin's ideals, and in defiance of Stalin's totalitarian state. This rivalry lead to a growing rift between Russia and Mexico to the extent that Mexico eventually sided with the United States of America in the Cold War.