The United States holds a veto over sales of Sweden’s JAS 39 Gripen fighter for one simple reason: every Gripen ever built runs on an American engine, and under U.S. export law, Washington decides where that engine — and therefore the jet — is allowed to go. For 25 years, that veto was invisible, because the United States always said yes. In 2025, it said no for the first time, signaling it would withhold the engine for Colombia’s planned Gripen…