They don't believe in the pledge itself much, no, and neither do I. But if you ask quite literally any American if they're patriotic and have pride in their country, I guarantee you they'll release an emphatic hell yes.
And we already have a well run country- we may complain about it's many shortcomings, but that number pales in comparison to almost any other country on the planet, and it's because of that, I think, that we are so patriotic. But it's little things like a pledge that go towards strengthening it. Like I said, the pledge alone doesn't do much, but combined with the plethora of other things that follow the same idea, Americans' sense of nationalism is greatly strengthened.