Bangladesh, July 11 -- For nearly eight decades, Europe has enjoyed an extraordinary strategic luxury: the ability to pursue economic integration and political reconciliation under the protective umbrella of American power. From the ashes of the Second World War to the end of the Cold War and beyond, the United States served as the guarantor of European security and the informal leader of the Western alliance. That arrangement enabled Europe to transform itself from a continent of recurring wars into one of unprecedented peace and prosperity.

That era is rapidly coming to an end.

Under President Donald Trumps second administration, Washington is redefining its relationship with Europe in ways that extend far beyond troop reductions or d...