If you can't afford a ticket to the world, the next best thing is a ticket to the Edinburgh Festival. In a single August afternoon here you can wander from Colombia to Russia, taking pit stops with the Lady-Boys of Bangkok and the Soweto Children's Choir. The Edinburgh Festival is internationalism made flesh, the whole world in one fringe. The loudest (and most entertaining) clash happening here is between two nations that gape at each other in mute incomprehension: liberal blue-state America, the Land of the Free, vs conservative red-state America, Land of the Fee.
Liberal Americans have hurried here to scream about the hefty chunk of their country - the Bush base - that believes gay marriage and Kyoto are threats to civilisation but chemical weapons and torture are not. Doug Stanhope is the dishevelled, decadent voice of this free America. He staggers on stage glugging beer, saying, "I'm pretty sure funny's at the bottom here, hang on." His routine tumbles out in a drug-haze, his speech centres blown by decades of chemical over-stimulation. "All illegal drugs are medicinal. Boredom is a disease, drugs are the cure," he whimpers. He then begins to talk about a time a gaggle of anti-abortion activists placed a photograph of a foetus under his windshield. "I guess it's supposed to disgust you into not having an abortion," he drawls. "As if childbirth would look good on a poster. Some mutant coming out of your genitals covered with mucus - yeah, I really wanna see that over dinner."
But Stanhope swiftly noticed that the organisation had left a contact number at the bottom of the flyer, in case you were inspired to join them. "So I called them up and explained that they were the worst kind of child pornographers known to man. Putting pictures of naked children on windshields. Don't you know how many pre-term necrophiliac child molesters are out there? You could have photo-shopped a bikini on and stencilled in a tasteful one-piece, but no. You, sir, are a deviant!"
The show is a cold, bracing bath in Stanhope's hatred of a mutant vision of America as Jesus-Land. He fears this clucking, tutting America is infecting even New York and California's "Google-for-brains" young. "Every older generation hates the younger generation, but it used to be they said the young were getting more and more deviant. 'If we wanted fun, we went to a barn-dance', they'd say. We're the first generation of old people bitching that the young are so tame. Look at these kids - we used to do crack. These pussies just drink Red Bull and go on the patio to smoke. The closest they've come to a fist fight is in a chatroom. 'You looking at my girlfriend? Well I'm going to delete you from my MySpace friends list.'"
Another equally brilliant American stand-up comedian, Rich Hall, is also talking about the Grand Canyon running between red and blue America - but instead of doing it in his natural medium, he has written a strange, slightly awkward play. Levelland at the Assembly Rooms presents a uniquely American dystopia: chaos in the Middle East and a string of hurricanes along the Gulf Coast have sent oil prices soaring to $10 a barrel. Cars are rusting in their suburban driveways from sea to shining sea. The lights are going out all over America.
We witness this American meltdown from the studio of Wayman Tisdale, a West Texas shock-jock played by Hall himself. Radio shock-jockery is a distinctively American art-form, a product of the glories of the First Amendment and the paranoid style in American politics. Wayman's callers declare that the US should just "level Crapistan and grab the oil", alternately blaming the Jews and the "yellows" for planning this disaster. Wayman disagrees, arguing that "Opec is a terrorist organisation" - until an armed burglar breaks in declaring that he can divine the presence of fresh stocks of oil by sniffing the air.
The thriller that ensues doesn't really work, since it depends of chunks of flat exposition delivered in a gabbled yell. But the play offers a horribly apt symbol for the Bush years - a crucifix doused in oil - and one brilliant joke. Wayman is lamenting the spread of homogenous, amoral corporations across the globe, and asks, "Ever been to the Vatican? There's a McDonald's right opposite. You are sitting in McDonald's enjoying your hamburger and you are forced to stare at this annoying franchise that has been responsible for poverty, genocide and 2,000 years of kiddy-fiddling."
Once you have gorged on American culture, your world tour along the Royal Mile can take you to a hundred other countries, but the American influence is always there. I picked Palestine and Australia as my next destinations, only to end up haunted by Red America. My Name is Rachel Corrie at the Pleasance is the simple, true story of an American girl who travelled to the occupied Palestinian Territories to join the International Solidarity Movement. She stood in front of tanks and bulldozers driving towards the homes of innocent Palestinian civilians, until one day the bulldozer did not stop. An Israeli soldier crushed her to death.
It's very hard to criticise a play with an urgent and worthy topic like this without seeming to criticise its subject. But while Rachel Corrie was a brave and brilliant person, this play - directed by Alan Rickman - is an oddly grating disappointment. This should be the story of how a privileged white girl discovered the suffering of the Palestinians and died for them. But on this stage, Corrie barely interacts with any Palestinians. The only ones she mentions are a few children - a very revealing illustration of how the authors infantilise and silence the Palestinians, reducing them to a picturesque backdrop for a white girl's tragedy. This isn't their story - it's the story of a hippie, dippy chick who wants to be a poet and dies young. Rachel Corrie's life was a testimony to internationalism, but this play makes it look like a monument to narcissism.
The darkest and most incendiary politics on the fringe come from the brilliant Australian playwright Vanessa Badham. Most new writers cautiously cling to the domestic and the local; by contrast, Badham's new play Persae swings from the Oval Office to the battlefields of Iraq to a bombed-out Sydney reeling from the suicide-murder of Prime Minister John Howard.
Persae is a modern-day adaptation of the oldest play in existence, The Persians by Aeschylus. He wrote it as a warning to his fellow Greeks about the need to avoid imperial adventures, by depicting the disastrous war in which the Persian king Darius invaded Greece in order to seize the country's silver-mines. He was beaten back by a fierce insurgency, only for his son Xerxes to pick up the fight 10 years later with an even larger invasion force - and an even larger disaster. No contemporary parallels there, then.
Badham shows the story through the eyes of Barbara Bush. As the play segues from Aeschlyus' metre into the glib soundbites of America's Foxed-up media, Barbara is haunted by charred veterans of the first Gulf War. Forced to see what becomes of the Purple-hearted, Barbara veers off-message - and a bomb explodes in Australia. Stumbling around the charred wreckage of Sydney, Badham's characters ask - did we really imagine we could wish violence on the Middle East and it would never come home? One asks, "Did you think we would get the privilege of a bloodless war just because we're better armed?" Even when Badham's politics are open to serious dispute - I disagree with swathes of it - and her ambition runs ahead of her abilities, she still offers a more invigorating slap than the wet whinging that passes for so much political theatre.
Doug Stanhope, George Square Theatre (0131-226 0000), to 27 August; 'Levelland by Rich Hall', Assembly Rooms (0131-226 2428), to 28 August; 'My Name is Rachel Corrie', Pleasance Courtyard (0131-556 6550), to 28 August; 'Persae', Smirnoff Underbelly (08707 453 083), to 27 AugustReuse content