What did the U. S. (Texas) and Mexico not agree on that eventually led to the start of the war

In 1846, a dispute over the border between Texas and Mexico resulted in armed conflict, and the Mexican–American War began

Explanation:

The Mexican army attacked them. The main cause of the war was the westward expansion of the United States. All through the 19th century Americans believed it was their right to expand westward.

c. extended rights of citizenship to new groups