Why did American diplomacy with Mexico become more aggressive and what was the result?

American diplomacy with Mexico became more aggressive in the mid-19th century due to a combination of factors, including the desire for territorial expansion, economic interests, and the ideology of Manifest Destiny. This culminated in the Mexican-American War (1846-1848), where the U.S. sought to acquire land, leading to significant territorial gains such as California and New Mexico through the Treaty of Guadalupe Hidalgo. The aggressive stance heightened tensions between the two nations and contributed to longstanding issues in U.S.-Mexico relations. Ultimately, it set a precedent for U.S. interventionist policies in Latin America.