Not particularly "US vs. Europe"-style war based, but I think a Great Depression that goes worse and leads to the US imploding into civil war can spur different countries supporting different sides, i.e. USSR supporting Communists and etc.
Providence has truly smiled upon the US by giving it friendly neighbors on both land borders.
Maybe Europe goes commie by 1940 with Rosa leading a red Germany and Trotsky a red Russia a fully United Bolsheviki Europe would have the industrial power and political will I think to pull off a "final glorious war of liberation agains the last imperialist power."