Answer:
Option A is the right answer.
Step-by-step explanation:
The main impact of the acquisition of northwestern territory is that it served as a main cause of American Mexican war. America’s manifest destiny was achieved and rewarded by the war that was waged between America and Mexico.
United States desire to acquire the entire west, urged them to enter the territories of Texas which belonged to Mexico. This hostile invasion created apprehensions in Mexico and they feared of losing Texas.
This American Mexican war created border dispute between America and Mexico which resulted in cession of vast lands. It was an unreasonable conflict based on the Belief that America was provided with Divine right to expand in order to attain glory in the world (Manifest destiny).