By trusting the US, we handed Trump a kill switch. Yet Europe’s digital sovereignty is an achievable goalThe French judge Nicolas Guillou knows exactly how deep Europe’s dependence on US tech is. Guillou and his colleagues at the international criminal court are under US sanctions. They can no longer use e-commerce, book hotels online or hire a car. Their home smart devices ignore them. Credit cards from European banks no longer function, because Europe has still not developed its own EU-wide payments system, so most electronic purchases go through Visa and Mastercard. Converting euros to foreign currencies is extraordinarily difficult because everything passes through dollars. Living in Europe is no protection against Donald Trump bricking your digital life.This dependence is not limited to mod-cons. Last year, the chairman of the Danish parliament’s defence committee said that he regretted his part in Denmark’s decision to buy US-made F-35 fighter jets: “I can easily imagine a situat...