Name two undeclared wars

The Vietnam war and U. S Civil War

I can name more than two for you, if we are talking about the U. S. A.:

(Take note, that I listed wars that took place after the 70s, if I seem to remember)

First Gulf of Sidra Incident

Lebanese Civil War

The bombing of Libya

Iran-Iraq War

Invasion of Panama

First Gulf War

Somali Civil War

Bosnian War

Operation Uphold Democracy

Bombings of Afghanistan and Sudan

Kosovo War

War on Terror

Second Liberian War

Lord's Resistance Army Insurgency

Libyan Civil War