Because of nuclear weapons, only "limited wars" could be fought; limited to conventional non-atomic weapons. WW2 was the US's last declared war; and atomic weapons did NOT exist when that war was declared. A declaration of war implies TOTAL war; which uses ALL available weapons to win! Total declared wars cannot be fought in the atomic age, without risking "mutually assured destruction." Hence, the cold war; a military stand-off between two sets of nuclear armed nations.
US Civil War & Vietnam War.
Congress ; see related link .
The US has officially only lost one war: The Vietnam War.
Officially, the North Vietnamese. Tacitly, The Soviet Union and China.
The countries that were actually "physically" involved, and were bombed or had US aircraft crash into them, whether they were "officially" in the war or not, were: Lao's, Cambodia, North Vietnam and South Vietnam.
An atomic power can't declare war, that would imply using nukes. The last time the US declared war was in WWII. And nukes didn't exist then.
The United States Congress officially declared war on Germany on April 6, 1917. President Woodrow Wilson asked for a declaration on April 2.
US involvement in Vietnam started in the early 1950's. We were there as advisors. We officially became part of the battle in 1965 and pulled out in 1975. It is important to understand that President Johnson did NOT have Congressional approval to declare war, therefore we were not officially at war. ALSO when we pulled out - because of not being 'at war' with Vietnam - we did not lose the war. We officially pulled out and chose not to continue fighting.
The American Civil War (US Civil War), like the Vietnam War a hundred years later, was an undeclared war. Another words the Confederacy was not recognized as an independent nation by the US Government.
Man's best friend was in Vietnam; over 5,000 of them. 3,747 of whom were documented. Approximately 73 US servicemen assigned as dog handlers and 43 war dogs were killed in Vietnam. US military K9s were officially classified as military working dogs in Vietnam.
The US military used about 5,000 war dogs (officially designated Military Working Dogs) during the Vietnam War, and approximately 10,000 US servicemen performed the duties of "dog handlers" in the war.
President Truman officially integrated the US Military in 1947 (along with creating the US Air Force-Separating it from the US Army). The Korean War (1950-1953) was the FIRST US war in which the US Military was officially integrated.