I do not agree with this statement. I would argue that foreign policy helped to bring about social unrest, but that most of the social unrest came from domestic factors.
It is certainly true that the Vietnam War, in particular, led to a great deal of unrest. People felt that the war was immoral or unnecessary or both. They protested the war, leading to tensions between themselves and those who defended the war.
However, this was only a small part of the social unrest of the 1960s. One major factor in the unrest was race relations. The Civil Rights Movement was not largely caused by external involvement. Instead, it was caused by racial injustice on here at home. Even so, it led to some of the greatest unrest of the decade. The counterculture was also not caused mainly by foreign affairs. Instead, it was largely caused by the fact that many young people were disillusioned with American society and values in general.
Thus, some of the greatest unrest came from factors that were not closely connected to foreign involvement.