As much as people complain about the EU, its the last western polity that is functioning to some degree of normal.

To put it politely, America is just not, at this moment in time, with a predictable actor with rational self interest.

If things continue to fail, then its simple to assume we return to the spheres of interest stage of things, at which point the EU still functions as a bloc which everyone trades with.

Plus, American GDP figures are matched with a K shaped economy, and a population with a deep sense of unease and unhappiness.