Oh Bummer.

And so the honeymoon ends.
Never mind what US presidents get up to domestically; we have a hard enough time working out the subtleties of relative right and wrong in a system with two competing right-wing parties, especially through the fuzzy filter of American media. So, barring something spectacularly demented in their own backyard (Bush was good for these too) Europeans can usually only judge them when they venture out into the world. And Obama's been on the loose in Europe for long enough in the last week that something had to give. In short, he's suggesting that Turkey should be welcomed into the EU.
Naturally, Uncle Worzel Gummidge across the pond is thinking with his defence head on. It's surely safer to bring into the fold a populous Muslim country that's in a highly strategic position, bordering Iraq, Iran and the Caucasian states, and also a NATO member to boot. Unfortunately, it's a bit more complicated than that and for once Obama isn't demonstrating too much tact towards his EU hosts with the timing of this support.
The fundamental problem with Turkey's membership isn't one of religion, or at least it doesn't have to be. The EU already has plenty of Muslim citizens and, besides, Turkey has been a secular state ever since its foundation, despite effectively its entire population being Islamic. Nor does it have to be the economic issue. If granted membership, Turkey would of course be a drain on common resources in the form of subsidies and regional aid. But it also has a higher GDP per capita than the existing member Bulgaria, for example, and would provide a large market and labour pool, both more accessible than now, for the rest of the EU. No, it boils down to the perennial question of human rights. Amnesty International have still very much got Turkey on their blacklist, but there is an abundance of more anecdotal evidence to pin on Turkey's record. Not to mention the fact that they continue to deny culpability for the Armenian genocide. Atatürk may have dragged the nation kicking and screaming into the 20th century, but peoples take longer to change than laws do.
As for a suitable riposte to the Americans, let's just start harping on about the North American Union and insist they invite Cuba into it. How'd you like them apples, as they say.