The United States army has lost several wars.
Since the early 50s the US Army lost or withdrew from following battles with no or little success.
Korean War, Korea 1950-1953
Second Indochina War, Vietnam 1953-1975
Bay of Pigs Invasion, Cuba 1961
Operation Restore Hope, Somalia (Multinational for US victory later) 1992-1994
There are also several wars going against different groups and organizations.
Notable.
War on terror (al-Qaeda, Taliban, Al Shabaab, Hamas, Hesbollah etc.) 2001
LRA Insurgency, Central Africa 2011
The south lost the U.S Civil War.
The US has officially only lost one war: The Vietnam War.
NO, the US lost the Vietnam war
Red Cloud's War or The Bozeman War
The unity of the U.S. currency was lost with the Civil War.
It is generally accepted that the USSR lost the Cold War, not the US.
In warfare the war which is most costly to US lives is the US Civil War.
civil war
It lost almost half its territory.
52 subs were sunk (lost).
False. The US lost the Vietnam War. The South, whom the US were supporting, had become very corrupt and the US public withdrew their support for the war. The US withdrew and retreated, so their objective was not achieved, and therefore was lost.
The US lost 58,000 soldiers and around 111-135 billion dollors lost.