Who is the only American whose name is engraved on the Arc de Triomphe in Paris?

This has been a tough one. But I need to ask if being an 'honorary citizen' counts? If so, then I would say that Marquis de Lafayette is the answer. His name is inscribed on the 3rd column of the Northern pillar.

https://en.wikipedia.org/wiki/Gilbert_du_Motier,_Marquis_de_Lafayette

https://en.wikipedia.org/wiki/Names_inscribed_under_the_Arc_de_Triomphe#Northern_pillar

It is definitely Gilbert de Motier, Marquis de Lafayette. He was granted citizenship of Maryland, Massachusetts, Virginia and Connecticut.

Maryland's legislature honored him by making him and his male heirs "natural born Citizens" of the state, which made him a natural-born citizen of the United States after the 1789 ratification of the Constitution.

So there is no doubt that he is NOT just 'honorary citizen'. De Motier himself quipped that "that he had become an American citizen before the concept of French citizenship existed."

Sources:
https://www.nytimes.com/1919/09/07/archives/lafayette-citizen-of-america-maryland-legislature-conferred.html
https://rmc.library.cornell.edu/lafayette/index.html

A hint:Look for a South American freedom fighter who fought for France during the Revolutionary Wars.

So, it's Francisco de Miranda, a Venezuelan military leader born in 1750. In 1791, Miranda took part in the French Revolution as a marechal de camp (general officer) in the French Revolutionary Army.

https://en.wikipedia.org/wiki/Francisco_de_Miranda

His name is inscribed on the Northern Pillar (Column 04) of the Arc de Triomphe.

https://en.wikipedia.org/wiki/Names_inscribed_under_the_Arc_de_Triomphe#/media/File:Arc_de_Triomphe_mg_6823.jpg

This might be a technicality, but "American" to people from North and South America, means someone from the United States of America. The rest of us are "Canadian", "Mexican", "Venezuelan" etc., but NOT "American", unless you add "North" or "South" as a prefix. The correct answer to your question as written, to me as a Canadian, would indeed be Lafayette, the honorary American citizen.

This is *trivia*, so we can call Miranda an American. :) Notice that the question doesn't ask for an American *citizen*. (Try defining "Yankee"!)

One of Merriam-Webster's definitions of "American" is "a native or inhabitant of North America or South America."
https://www.merriam-webster.com/dictionary/American

"Miranda's notable participation in [the French Revolution] granted him the honour of being the only American whose name was inscribed on the Arc de Triomphe in Paris."
https://en.unesco.org/memoryoftheworld/registry/387

Miranda did all kinds of heroic stuff in multiple countries; look him up in Wikipedia.

Here's a photo with his surname engraved on the Arc de Triomphe; look on the left side. He was from Valencia, Venezuela.
https://www.gettyimages.com/detail/photo/arc-de-triomphe-detail-royalty-free-image/665554910