Disengagement would be a risky strategy but, potentially, one with significant payoffs.
Steve, a nice article but with two significant caveats.

1) I don't think you've established that Islamophobic sentiments have become dominant within the American political establishment. It might have found a receptive audience in large segments of the American population, but that's a far cry from actually becoming influential over either the policy community or the political community as a whole. Americans generally don't vote on foreign policy, and while there is a lot of free-floating hostility out there that can coalesce around cultural markers, that's not the same as formulating a new foreign policy direction. American alliances with Muslim countries like Turkey and Saudi Arabia are deeply embedded. Anti-Americanism in both places has run far higher in the past than Islamophobia has in the U.S., but that has not prevented Turkish or Saudi elites from deepening the alliance further for much the same reason --- domestic constituencies often have greater priorities than the relationship with the U.S.

2) Even assuming your point about anti-Muslim feelings becoming a driving force in American foreign policy, I cannot see how this leads to inevitably to disengagement/containment or smaller defense budgets. There are enormous domestic political constituencies invested in larger defense budgets. A forward-leaning Islamophobic American foreign policy is also possible, based on aggressive military action against supposed threats (which would now extend to a far greater spectrum of Muslim 'enemies') and a greater tolerance for civilian casualties.