smoghat - Your wording hints at being the original poster we're trying to convince, which you're not. Also, if someone is willing to change their investing style because of your personal impressions of international markets, they're already in trouble. Investing decisions on emotion are bad enough - on someone else's emotion is even worse.
Bogle and Buffet both suggest the S&P 500 is all you need, thanks to the international reach of US corporations. You could also argue the world has become so interconnected that US and international markets are more correlated today than in the past. That's at least based on characteristics of US companies rather than fear.
The problem, especially relevant to OP, is seeing a 60% emerging markets portfolio. It suggests whatever succeeds most be a priority. When US makes 4% a year and Europe earns 14% a year, OP will be sorely tempted to switch allocations at the wrong time. Chasing performance can translate to buying high each time.