All of the continents, Europe, Asia, Africa, Australia, North America, and South America, with the exception of Antarctica, were involved in World War I.
England and America
Since America was only involved with one Japanese War you must be referring to WWII. In that case, Japan attacked America with airplanes at Pearl Harbor on December 7, 1941. That's why Americans got involved.
The Vietnam war. Or the Resistance War Against America.
It got America involved in the war. Who knows what would have happened if they didn't get involved.
The Korean war
Given that the revolutionary war is the war that created the USA, it could be said that the USA was involved from the start.
russia
Spain and America
it was 2004
America did get involved
April 1917
The bombing of Pearl Harbor.
it wasn't
america!
German submarines were in the US east coast of America so that was the final straw for America, so then we declared war
Officially, no, America is not in a war. In my opinion however you could say that the USA is involved ( by no choice of their own ) in a war with radical Muslim terrorists.