How did American foreign policy change as a result of involvement in Vietnam?

One of the most significant political effects of the Vietnam War was the change in American Foreign Policy. America entered the Vietnam War as the world's leading superpower but left Vietnam defeated after the longest and most debilitating war both nations had ever seen.  The war left America with a crippled economy and unfair balance of trade.  The loss of American lives was significant at 58,000 soldiers and the harrowing loss left Americans back at home divided and mistrustful of the government.  The war also damaged America's long-standing reputation as a swift, competent and powerful leader. As a result, American leaders in the 70s, 80s, and 90s were reluctant to send troops overseas unless absolutely necessary.  This reluctance, known as the United States' "non-intervention policy", still impacts Foreign Policy today as the American government continues to proceed into other countries with caution, making sure they have "sold" the American public on the need to intervene and when they believe there is a high probability of a quick, inexpensive win.

Part of America's change in foreign policy was a willingness to use special operations soldiers in advancing American interests. In an attempt to drive out the Viet Cong from the Ho Chi Minh Trail, the United States invaded Laos and Cambodia. The Viet Cong were still able to use the trail, and the American invasion destabilized these two countries, thus making the postwar refugee situation worse.
As a result of Vietnam, the American people did not wish to send troops into protracted wars. Policy makers declared that they wanted "No more Vietnams!" The military had very short, successful missions in Grenada and Panama, and the CIA provided assistance to Afghan fighters during the Soviet-Afghan War, but the American people did not want any major wars. The first major war that took place after Vietnam was the first Gulf War in which the United States used its technology and military might to overpower the Iraqi Army. This war was over in a matter of hours and was quite popular in that it had a clear objective: remove Iraq from Kuwait. The United States is still seeking out answers to fighting guerrilla soldiers (as evidenced by its actions in Afghanistan and Iraq), but since the Vietnam War, there has been more of an attempt to have a clear enemy and a clear objective to sell to the American people when it comes to foreign policy, especially in armed conflict.