"I'm not sure the next summit will even be possible,"
That is how far USA has fallen from grace in Latin America. What the prostitution scandal shows is given an opportunity Americans - common Americans - would find it hard to resist exploitation of flesh, drugs and market of Latin America. Add to it, isolation of President Obama in legalizing drugs. It is easy to understand in an election year President Obama cannot simply back legalization of drugs which basically shifts the burden of drug war from producers to consumers i.e. those Americans who are addicts and the American System which sustains this consumption.
It is possible that in his second term Obama would back admission of Cuba in OAS. But in an election year - that is hard and hence complete isolation of USA & Canada on that. Traditionally conservative and pro-USA Chile might come along USA in this regard; but by and large most countries in Americas want Cuba to be in. And reality is more 'good is likely' to come by Cuba joining OAS rather than being a pawn of China. But Conservatives in USA are unlikely to understand any of this. Practically they would go for division of Americas between a group of USA, Canada, Columbia (though even it backed Cuba admission) & Chile (where the conservative president is loosing the altitude fast) and rest of the countries in another group led by behemoth Brazil. Ironically, Paul Ryans of GOP would strike a chord with Brazilian President when she complains about Bernanke Fed monetary easing. Except that, countries of Americas are likely to find that Romney Administration will be not be any easy to deal with. All that means is the way American Politics is structured today, America is simply incapable of stopping its waning influence in Americas.