really?
one in the last 20 years - Iraq II - sad, yes
one more in the 20 years before that - Iraq I (did we really start that one?)
one more in the 20 years before that - Vietnam (clearly not started by the US, but escalated)
one more in the 20 years before that - Korea (again - we just joined in a war that already begun)
one more in the 20 years before that - WWII (you're right, we shouldn't have gotten involved - left Europe to the Nazis and all of Asia to the Japanese Empire)
Yes, really.
How about the aggression against little countries:
. LEBANON l958 Troops, naval Army & Marine occupation against rebels.
. PANAMA 1958 Troops Flag protests erupt into confrontation.
. VIETNAM l960-75 Troops, naval, bombing, nuclear threats Fought South Vietnam revolt & North Vietnam; one million killed in longest U.S. war; atomic bomb threats in l968 and l969.
. CUBA l961 Command operation CIA-directed exile invasion fails.
. PANAMA l964 Troops Panamanians shot for urging canal's return.
. DOMINICAN REPUBLIC 1965-66 Troops, bombing Army & Marines land during election campaign.
. CAMBODIA l969-75 Bombing, troops, naval Up to 2 million killed in decade of bombing, starvation, and political chaos.
. LEBANON l982-84 Naval, bombing, troops Marines expel PLO and back Phalangists, Navy bombs and shells Muslim positions. 241 Marines killed when Shi'a rebel bombs barracks.
. GRENADA l983-84 Troops, bombing Invasion four years after revolution.
. VIRGIN ISLANDS 1989 Troops St. Croix Black unrest after storm.
. PANAMA 1989 (-?) Troops, bombing Nationalist government ousted by 27,000 soldiers, leaders arrested, 2000+ killed.
. IRAQ 1990-91 Bombing, troops, naval Blockade of Iraqi and Jordanian ports, air strikes; 200,000+ killed in invasion of Iraq and Kuwait; large-scale destruction of Iraqi military.
. HAITI 1994 Troops, naval Blockade against military government; troops restore President Aristide to office three years after coup.
. AFGHANISTAN 2001-? Troops, bombing, missiles Massive U.S. mobilization to overthrow Taliban, hunt Al Qaeda fighters, install Karzai regime, and battle Taliban insurgency. More than 30,000 U.S. troops and numerous private security contractors carry occupation.
. IRAQ 2003-? Troops, naval, bombing, missiles Saddam regime toppled in Baghdad. More than 250,000 U.S. personnel participate in invasion. US and UK forces occupy country and battle Sunni and Shi'ite insurgencies. More than 160,000 troops and numerous private contractors carry out occupation and build large permanent bases.
. HAITI 2004-05 Troops, naval Marines & Army land after right-wing rebels oust elected President Aristide, who was advised to leave by Washington.
These are only instances where the military was involved directly, leaving out things like overthrowing democracy to install the Shah of Iran in 1953 (admitted to by President Obama). Except for Cuba in 1961, but the whole thing was put together by the Americans.