After a few days of researching post-revolutionary Mexican politics and coming up with a feasible way to make this happen (basically accelerating the processes that happened in real life around WWII), here is a fleshed out Mexico.

Name: The Federal Republic of United Mexican States 
Flag:
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[img]https://upload.wikimedia.org/wikipedia/commons/8/8f/Flag_of_Mexico_%281934-1968%29.svg[/img]
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Territory: Modern-day Mexican borders with the Panama Canal Zone (I don't really have the tools to make a map)
Government Ideology: Socialist Constitutionalist
Leader: President Enrique Hernandez
Rough Population: 28 million
Capital: Mexico City
History: The Mexican state has historically struggled with economic woes, particularly in the post-revolutionary era before the Great Depression. This meant that, when the American stock market crashed in 1929, the Mexican economy was arguably "too poor" to feel any significant effects. Businesses were mostly owned by foreign countries, mostly American, and the population was settling from a violent revolution and were tending to themselves. Society was adopting the views of socialist figures in Europe as a way to utilize the community to overcome economic barriers, and grassroots figures quickly became popular in small farming towns. The Mexican government itself entered a phase of restructuring at the end of the 1920s, ending up with an agenda dedicated to populism and a socialist interpretation of the Mexican constitution as a response to the economic woes.

The United States to the north was quickly falling apart under the Hoover administration, employing little to no effective relief measures as it did in reality. The Mexican government, under the control of Plutarco Elias Calles (who was not the president but governed from behind the scenes during a period known as Maximato) quickly recognized this as an opportunity to expand Mexico's might. American businesses were going bankrupt and were rapidly being sold to the Mexican national government. Oil infrastructure, factories, farms, and everything else became nationalized and quickly utilized to improve the Mexican economic situation. Calles, a known authoritarian and nationalist, enacted several relief acts designed to boost the Mexican economy. From 1929 to 1934, when the Maximato period ended, reforms produced a modern and productive Mexican state. The so-called Mexican Miracle, occurring in our timeline around the 1940s, had kicked off ten years earlier.

Oil production, nationalized from American companies, produced huge amounts of revenue and paved the way for increasing amounts of industrialization. Investments from foreign countries, most notably the Soviet Union under Stalin, were taken by Mexican leaders in the immediate wake of the Maximato period. This helped establish Mexico's position as a rising power in the Latin American world where Mexican exports quickly outpaced American goods in both quality and cost, as the American factories began to suffer more and more. To couple this, Mexico's farms were rushed with an influx of demand by 1934 as the first of the Dust Bowl droughts crippled the American agricultural machine in the midwest. Corn and wheat, once sold in bulk by American farms, became a staple export of rural Mexico. To deal with the increased trade around Latin America and the Pacific, the Mexican government purchased merchant vessels and warships from the United States, forming the core of a modernized Mexican Navy.

Trade relations between Mexico and neighboring countries improved as a result of the rapid economic successes in the wake of the United States' decline. Japan in particular became a customer of the Mexican oil industry, finding cheaper fuel for its war machine than could be offered by the United States at the time. Latin America, still struggling economically and engaging in bush wars against each other, welcomed parties of Mexican Army peacekeepers who would deploy in an expeditionary capacity to cool tensions and secure borders. Germans, fleeing their civil war, emigrated to Mexico in larger numbers, bringing their technical and professional knowledge with them. By 1936, Mexico had become a regional power and a champion of socialist progress in Latin America. The president-elect, Enrique Hernandez, became looking towards expansion. He reasoned that Mexico could spread its influence to the smaller countries in Latin America, if only because he held a deep desire for Mexican resurgence.

When it became imminent that the United States could no longer control its territories, Hernandez acted quickly. He approached desperate American government officials and bought large amounts of equipment for use in the military and industrial realm. He pleaded for the Mexican migrant workers to return to Mexico for greater opportunity, and quickly hedged his bets on a total collapse of the American state. His largest purchase, however, was a shock to the world: the Panama Canal, bought from the United States for the incredibly light sum of twenty million dollars. Almost as soon as the deal was finalized and the Mexican flag was hoisted over the canal zone, the Treaty of Washington DC dissolved the federal American government and taking Mexico off the hook for its rapidly increasing debt payments. Hernandez shrewdly played the legal aspects of the deals, now owing no money to the Balkanized states left over by the dissolution. While many in the former US resented Hernandez as a "wetback thief", Mexico was better off than it was just a year before.

Mexico stands poised to continue its miracle in the coming years as it becomes apparent that the United States is no longer there to check its growth. President Hernandez, man of the people, is determined to showcase the Latino resurgence in the modern era.