I'm new here and this is my personal scenario for the future. Warning, it's biased and might be stereotypical. This is a work in progess and will be expanded on.
In this scenario, things change when a new Republican president is elected to office in the US, Han Muller. A German born immigrant, Muller becomes the first European president. His leadership though, is tested when Mexico officially folds and is taken over by many Cartels and gangs.
The Cartels mostly kill each other off and turn Mexico into a anarchy zone, but the US doesn't step in just yet. Other countries try to claim parts of Southern Mexico, El Salvador taking part of the gulf as it's territory. This leads to conflict between El Salvador and the Gufl Cartel, the Gulf Cartel taking heavy losses and being forced out of their territory. About 500 are killed in the first border clash.
After the Salvadorians kicked the Gulf Cartel from the Gulf of Mexico, Los Zetas stepped in and attacked Salvador's new territory. Using guerilla tactics to take the land of their former rival. Now the death toll is up to 1,000, and the Los Zetas Cartel is the largest and most powerful in Mexico, and officially takes over the government.
President Muller officially releases a statement, saying that the US will not fight Los Zetas but is neutral and the countries are not allies.
More border wars happen, this time between Zetas and Gulf. The total death toll is up to 1,200 by now. The US cracks down on border control to try and keep the war from spilling into the southern part of the States, and immigration from Mexico is put on a tempoary ban until the fighting stops.
A small uprising starts to fight the new government, made up of former military soldiers. It was quickly crushed by multiple gangs.
Near the end of the month, the former Mexican armed forces spread out and some join the United States as refugees. Others keep fighting on the west coast of Mexico.
The US starts researching nuclear power and plans to start using it in a couple of years, starting now with construction of test plants in remote cities. Small islands off the pacific are the main test plant locations and the project is greenlighted for the next couple years.
The US also approves a new project to expand Amtrak's high speed rail system to the midwest, starting with building a new Acela line between New York City and Chicago.