A liberal comedian and GOP princess walk into a bar …

Admittedly, not the greatest setup for a joke. But the farcical premise plays out repeatedly in “America, You Sexy Bitch”— the he said, she said account of Michael Ian Black’s and Meghan McCain’s meandering pilgrimage across the U-S-of-A.

As far as political tell-alls go, the book is pretty tame.

Bottom line: No racy sex (though the road trippers do get screwed out of reliable air conditioning). PG-rated violence (target practice in Arizona). Nominal drug use (the pair smoke a bowl while touring N’awlins). And ample boozing. (“Meghan, of course, loves the French Quarter because she is unembarrassed to be seen among drunken white people. After all, a lot of the time she is a drunken white person,” Black quips.)

McCain told HOH that the entire trip, which took place in July 2011, was hatched and executed on a lark.

Black got the ball rolling by floating plans to do a “political book” to McCain via Twitter. The political odd couple started spit-balling concepts/destinations to McCain’s publisher, and before they knew it, they were barreling down the highway in a rented RV with a bare-bones agenda and no real idea what they were in for.

Along the way, they bicker, then bond, fume, then forgive.

Just don’t expect a fairy tale ending. The atheist funnyman does not find god. The 27-year-old conservative scion still clings to her guns.

They do, however, manage to shed some of the stereotypes they’ve long held about those across the aisle.

McCain, for instance, gains a new respect for outgoing Rep. Dennis Kucinich (D-Ohio).

“I start wondering why the hell Kucinich has not been able to catch on nationally in a more significant way,” she writes after an eye-opening exchange.

Black, too, falls under Kucinich’s spell. But what’s most surprising is his reaction to hanging with Sen. Lindsey Graham (R-S.C.).

“He is, and I can think of no better way to describe him, a hoot. The guy is just funny: deadpan and sarcastic. Within moments of his arrival, all of us are laughing,” Black relates about sitting down to dinner with Graham while visiting Washington, D.C.

According to McCain, Graham was always intended to be the ace up her sleeve.

“He’s like an uncle to me,” she said, stressing that’s why she insisted that the Southern charmer — who remains tight with her father, Arizona Sen. John McCain — join them for the group dinner at a local steakhouse.

To wit, Meghan told HOH that her father lobbied (and lost) against having dinner at the Capital Grille — “He thinks it’s a little expensive,” she explained — proposing they commune at the Monocle instead.

As for the frank drug talk, McCain maintains she’s only smoked marijuana “maybe” two or three times in her life. And while she’s unlikely to grace the cover of High Times anytime soon, she is absolutely for decriminalizing the currently controlled substance.

And she has no regrets about indulging in it either.

“I know it’s a risk. But I like sharing things,” the outspoken author asserted.

The book goes on sale July 4.