Europe risks ushering in a new era of protectionism by joining the US subsidy race.

Joe Biden's clean technology law has drawn the European Union into a subsidy battle that might spark a transatlantic trade war, just as the allies are banding together to counter Russia's invasion of Ukraine. Even as the US has grown increasingly antagonistic to the limits imposed by the World Trade Organization, the EU has always championed the global rules-based order. However, Biden's $500 billion in new spending and tax benefit....