Why did Britain Mexico oppose American expansion?

- Economic competition: Britain was the leading economic power in the world at the time, and it saw the United States as a growing economic rival. The British feared that American expansion would lead to increased competition for resources and markets, and that the United States would eventually eclipse Britain as the dominant economic power.

- Political concerns: Britain was also concerned about the political implications of American expansion. Britain had long been the dominant power in the Americas, and it saw American expansion as a threat to its own influence in the region. The British feared that the United States would eventually become too powerful and would challenge Britain's control of the Americas.

- Territorial disputes: Britain and the United States had a number of territorial disputes in the Americas, including the Oregon Territory, the Maine-New Brunswick boundary dispute, and the Texas Annexation. These disputes led to tensions between the two countries, and made it difficult for them to cooperate on other issues.

Mexico opposed American expansion primarily because it feared that the United States would eventually annex Mexico. Mexico had already lost a significant amount of territory to the United States in the Mexican-American War, and it was determined to prevent any further losses. The Mexicans also resented the way that the United States had treated them during the Mexican-American War, and they were not eager to become part of the United States.