James Fallows spotted something that everybody else seemed to have missed: Obama gave a speech last week (on health care, in this case), and didn't end it by saying, "God bless America." As Fallows explained earlier, America-hating crypto-commies like George Washington, Thomas Jefferson, John Adams, and every president through Jimmy Carter (himself an evangelical Christian) somehow managed to make speeches without this coda. Then as Fallows says, "Ronald Reagan began using the phrase to mean 'The speech is over now,' and ever since then politicians have seemed afraid not to tack it on, perhaps out of fear that we'll have the aural equivalent of phantom-limb pain if we don't hear the familiar words." The first presidential use was actually Richard Nixon's, but Reagan made it the thing you're supposed to say at the end of every speech.
These blessed politicians never say what they're actually intending, however. Is the speaker beseeching God to bless the country in the future, or is he just saying, "Hot damn, we're awesome!"? These days, Republicans do it because they dig it, in a "Team America World Police" theme song kind of way (NSFW, by the way), while Democrats do it because they're afraid that if they don't, they'll get called godless anti-American hippies. Which of course they get called anyway.
-- Paul Waldman