"I have German in my blood," President Donald Trump said, announcing his plans to visit Germany "maybe soon."
At their G7 meeting, the president also said he may soon undertake his first bilateral visit to Germany since taking office.
Merkel noted that people still have an obligation to "oppose all tendencies that seek to destroy democracy. This includes right-wing extremism."
"Must have been an 'awkward' moment for Angela Merkel to sit in ceremony as the Allies commemorated D-Day," Huckabee tweeted.
"In short, we have to work together rather than alone," the German chancellor told Harvard alumni.
The four-term chancellor said young Germans must face "the specters of the past."
First daughter-in-law and 2020 Donald Trump campaign adviser Lara Trump said Germany Chancellor Angela Merkel allowing in refugees is one of "the worst things that has ever happened to Germany."
"Any U.S. diplomat who acts like a high commissioner of an occupying power must learn that our tolerance also knows its limits," Wolfgang Kubicki, a deputy speaker of parliament said.
"I find it shocking that, in such a short time, he has managed to rip apart a relationship that has taken decades to build," said former German Foreign Minister Sigmar Gabriel.
At the same time, the French government assured its population it would never cede the once-disputed Alsace-Lorraine territory to Germany, nor would locals be forced to speak German.
The president has lobbed attacks at the leaders of some of America's closest allies, as well as those of international rivals.
"The threat of car tariffs is still on the table," said Eric Schweitzer, president of the Association of German Chambers of Industry and Commerce.
Harvard said the German chancellor will be its principal speaker at the ceremony next May.
"We know that we can only solve things through being reasonable and through dialogue," the German chancellor said.
"There are too many powers that wish to thwart us," French President Emmanuel Macron warned in a speech before the German parliament.
The German chancellor's support of French President Emmanuel Macron's calls for a unified European force came as U.S. President Donald Trump criticized the idea, mocking France's loss to the Nazis in World War II.
Heiko Maas believes the return of Democrats to power in the House of Representatives could lead to greater cooperation from the United States when it comes to international affairs.
"We have to protect ourselves with respect to China, Russia and even the United States of America," the French president said Tuesday.
Macron said Merkel "has never forgotten what Europe's values are and she leads her country with great courage," referring to her announcement as "extremely dignified."
The German chancellor informed the Christian Democratic Union of her decision after a disappointing result in Hesse regional election.
The chancellor said there was an "urgent need for further clarification" of the circumstances surrounding Jamal Khashoggi's killing.