There has been a long established consensus among American elites, and usually supported by a majority of the public, that the country must stay engaged abroad. Factors that can reduce public support have converged and are significantly impinging upon American interest in foreign affairs.
A majority (58%) of both Republicans and Democrats now say the U.S. should “pay less attention to problems over seas,” up from 49 percent in 2004. And from 9/11 to today, there has been a nine point jump among Americans who believe the “U.S. should mind its own business internationally.”
Republicans have traditionally been most in favor of a strong military and have since 9/11 supported America’s war efforts. But today, they join Democrats in favor of America coming home. The factors that tend to undermine American interest in foreign engagements are wars going poorly or expensively and bad domestic economies or massive deficits. 2011 has all the factors.
Partisanship always affects support for foreign involvement. Recently, Republicans had supported G.W. Bush’s interventions and Democrats backed Barack Obama’s. Democrats tend to be more dovish and have mostly quit Afghanistan and Republicans are supporting Obama much less than earlier in his term, including his foreign policy.
See Pew Research Center article: In shift from Bush era, more conservatives say "come home, America"