When was the last time usa declared war?
No context provided
What war was the last time the USA declared war?
World War II
No context provided
On what date was the last USA declaration of war?
June 5, 1942
Declaration of war by the United States
https://en.wikipedia.org/wiki/Declaration%20of%20war%20by%20the%20United%20States
The last time the United States formally declared war, using specific terminology, on any nation was in 1942, when war was declared against Axis-allied Hungary, Bulgaria, and Romania, because President Franklin Roosevelt thought it was improper to engage in hostilities against a country without a formal declaration of war.
Declaration of war by the United States
The last time the United States formally declared war was on June 5, 1942, against the Axis, in World War II. 