Whether Americans will continue to view government in a positive light will depend upon how well the government governs, on the patience of the populace, and on the effectiveness of the Republican opposition. The resurrection of the liberal belief in the efficacy of government is nonetheless encouraging.
Kazin writes about "the revival of Americanism" or patriotism on the left. Kazin argues that liberals have found fresh ways to express their love of country after 40 years of conservative branding that equated disloyalty with opposition to conservative policies. I'm not sure liberal Americanism has been revived -- we've always loved the promise of our nation and its core values of liberty, equality, and fairness -- so much as it has been unleashed. There wasn't much to celebrate while conservatives controlled a government that relentlessly undermined those values.
For that reason, I disagree with Kazin's conclusion that "after decades in denial, progressives have finally realized that they cannot lead America if America does not hold a privileged place in their hearts." There is nothing new about that realization, or about the liberal veneration of American values. It has simply taken some time for those who do not define themselves as liberal or conservative to understand that right wing policies are not the logical product of patriotism and do not advance the public good.
As Kazin notes, normally mellow liberals grew outraged by the worst abuses of the most recent Bush administration and vowed to take their country back. Whether "a liberal movement flourished" seems less clear. Frustration with lousy government flourished as voters came to realize that viewing government as the problem assured that government would be the problem. A government that can't respond effectively to natural disasters, that won't regulate the excesses of the financial industry, that sends soldiers to die on the basis of faulty intelligence, left voters convinced that there had to be a better way. I doubt that most of those voters embraced the L-word. Democrats represented an alternative and the center shifted its voting pattern. Whether it shifted philosophically (or whether it eventually will) remains to be seen.