Answer :
The Mexican-American War
Explanation :
The Mexican-American War allowed for the United States to gain and conquer the Southwest. This war also caused sectional conflict in the years leading up to the Civil War.
The Triple Alliance consisted of Austria-Hungary, Italy, and Germany.
That means that the correct answer is Great Britain, as that nation was not apart of the Triple Alliance. The Triple Alliance lasted from 1882 to 1915. It ended due to Italy entering World War I with the plan of hostility towards Austria-Hungary and Germany.
