What was once ours, shall be ours again.
Funny thing, in the book I'm writing about the shattered remnants of the United States (the one with the theme of humanity returning to older patterns after the gas dried up), Mexico is a relative bastion of prosperity and stability compared to it's northern neighbor(s). There's a war between Texas, which wants to rejoin Mexico with the rest of the southwest, and California, which had become a Chinese protected zone after the humilating American defeat in the Chinese-American war of 2042 (in the wake of the fall of the Chinese Communist Party and the subsequent rise of the Chinese Nationalist Party in elections, which idolized Chiang Kai-Shek and thus invaded Taiwan to reunite the Republic of China, triggering an American response), experienced large scale Chinese immigration, and was thus divided betwween the latino population that wanted to rejoin Mexico and the Chinese population that wanted to form a renewed Chinese Empire and Chinese protectorate on the other side of the ocean.
The Southeast, on the other hand, is divided between Communists and neo-Confederates. The north, and Europe, is a barren wasteland due to the advent of global warming and the changed course of the Gulf Stream.