The sad thing is, I can't think of anything that makes America different from other western countries anymore. The only thing that comes to mind is the freedom to own guns, and I don't know how long that one will last. Everything else already seems to have become the same oppressive hyper-regulated mess as everywhere else.
I would go with the separation of church and state, which is directly written into the Constitution. But GUNNNS it is.
Wouldn't also pick regulation as the problem.
I'd have picked lack of regulation on banks and the housing crisis. Citizens United. Patriot Act. American military adventurism. Deteriorating standards and rising expense of education and healthcare. A complete lack of bipartisanship in our politics. Our political discourse degenerating to the point that clowns like Trump even get a chance of taken seriously. A feeling of unfounded exceptionalism despite all-of-the-above.
But hey, the real problem is the old saw about bigger government.