What event did the annexation of Texas lead to that affected Oklahoma?

The annexation of Texas in 1845 significantly heightened tensions between the United States and Mexico, ultimately leading to the Mexican-American War. The annexation was contentious because Mexico still considered Texas a part of its territory, having lost it in a revolution in 1836. The war, which lasted from 1846 to 1848, was primarily fought over disputes concerning U.S. territorial expansion and borders.

The impact of the Mexican-American War on Oklahoma was substantial. Following the war, the Treaty of Guadalupe Hidalgo in 1848 resulted in Mexico ceding a large portion of its northern territories to the United States, including present-day Oklahoma which was part of the larger areas of New Mexico and Texas that were affected by the war. This territorial expansion made way for more settlers and contributed to the subsequent policy of Indian removal, which had profound effects on Native American populations in Oklahoma.

This context positions the Mexican-American War as a consequential event stemming from the annexation of Texas, distinctly qualifying it as the answer to the question related to the effects on Oklahoma.