Abstract: The United States is becoming more like Europe, and not in a good way. For a long time, the central difference between antitrust enforcement in the United States and Europe has been that the United States features not only public enforcement, but a vigorous system of private antitrust enforcement, while in Europe, public agencies have had an effective monopoly on antitrust enforcement. But that difference is on the verge of collapsing. We are achieving a form of convergence; but contrary to expectations, this convergence is not coming from recent European efforts to facilitate private enforcement, which have not yet overcome some serious obstacles on discovery and class actions. Instead, it is coming from the recent US Supreme Court decision in American Express v. Italian Colors Restaurant, which threatens to gut private antitrust enforcement in the United States by replacing it with ineffective forms of arbitration.