This Article compares European Union judicial federalism with the American version. Its thesis is that the European Union’s long-term goal of political integration probably cannot be achieved without strengthening its rudimentary judicial institutions. On the one hand, the EU is a federal system in which judicial power is divided between EU courts, of which there are only three, and the well-entrenched and longstanding member state court systems. On the other hand, both the preamble and Article 1 of the Treaty of Europe state that an aim of the European Union is “creating an ever closer union among the peoples of Europe.” The Article argues that central government courts and member state courts are not fungible. In close cases, the latter are more likely than the former to favor the member state’s interests. The EU’s approach to judicial federalism, with its heavy reliance on member state courts, will retard the political integration envisioned by the Treaty. The Article develops this thesis by comparing EU judicial federalism with the American variant, which differs from the EU system in two key respects: First, most issues of EU law are adjudicated in the member state courts. In the United States, a network of lower federal courts adjudicates many federal law issues. Second,the U.S. Supreme Court reviews state court judgments that turn on issues of federal law. The Court of Justice of the European Union does not review member state judgments, even on issues of EU law. The Article argues that these aspects of the federal system in the United States were indispensable to achieving and maintaining national unity. If the EU aspires to a similar level of political integration, their absence may prove to be a significant obstacle.