The US has fought several wars.
The Seminole Indians and the US.
The Vietnam War
WWII and WWI
If you mean the northern states, they fought in the Civil War. Other than that one time, the US has always been united. Any wars which involved the north, involved the entire US. The US has, of course, fought in two world wars and many other wars.
The US fought three wars to obtain land: 1. Indian Wars (1620-1890) 2. Mexican War (1846-1848) 3. Spanish-American War 1898
55,000,000
Which war? US fought many many wars.
Spain and the US.
yes
War of 1812
There isn't a specific answer to that