A solemn crowd of Germans and Americans — some soldiers, some civilians — gathered one sunny morning last month in the public cemetery in Kaiserslautern, in western Germany, where a grassy field holds the remains of 451 American infants.

Civic groups, service members and schoolchildren maintain the so-called Kindergraves, cutting grass and repairing headstones for the babies, born between 1952 and 1971 to military families stationed at the many bases nearby. Every May, they hold a ceremony in remembrance — just one expression of the multilayered German-American friendship that has undergirded the region for decades.

“We give thanks for the city of Kaiserslautern,” intoned Capt. Nathan Smith, an Air Force chaplain. “We are grateful that in a world wrought with pain, discord, war and grief, that we can stand together for the purpose of peace and love.”

That friendship is now being tested by President Trump, who has levied heavy tariffs against Europe and mused about withdrawing troops, or even leaving NATO. Meanwhile, recent polls in Germany show a significant drop in trust in the United States.

Even though Germany’s chancellor, Friedrich Merz, tried to tamp down the tension in a White House meeting with Mr. Trump on June 5, Mr. Merz has also urged European “independence” from the United States. The two are expected to meet at the Group of 7 summit in Canada, starting Sunday.