Why didn't the United States occupy the whole of Mexico during the US-Mexico War?

Because there is a great cultural and customs gap between the United States and Mexico, once the whole territory of Mexico is forcibly occupied, there will be great contradictions and differences between the American people and the Mexican people, and if it is serious, civil war will break out again in the United States. This situation will lead to a greater crisis in the United States, and Mexico is simply unable to fight against the United States. This is why we will not choose to occupy the whole of Mexico.

The geographical proximity between the United States and Mexico can be said to have caused the misfortune of the Mexican people. Because the Mexican people are close to the most powerful country in the world, there are great problems in the export of some Mexican products. This is mainly because all American products are superior to Mexico in quality and price, so the Mexican people don't have many opportunities for economic development.

Of course, from the perspective of cultural customs and concepts, it is absolutely the right choice not to occupy the whole of Mexico, because once it is forcibly occupied, it will make the whole situation in the United States turbulent. From what we have seen now, President Trump's efforts to stop illegal immigrants in Mexico can show how much harm these Mexicans have brought to American society, and even some drug dealers in Mexico sell drugs to the American people.

Therefore, it is America's own consideration not to occupy the whole of Mexico. From now on, it is a very correct choice not to occupy the whole of Mexico, because Mexico is incapable of posing a threat to the United States. And the United States can easily sanction Mexico.