In the United States, I’d probably name Oregon City, the famous end of the Oregon Trail and the first city founded west of the Rocky Mountains during the pioneer era. Its population is only 37,000.
For France it’s probably Vichy, infamously well known internationally for being the capital of the French pro-Nazi government during the Occupation. Only 25’000 inhabitants.
Nice one, didn’t think of that ! I suggested the one-letter town Y (population : 89), which is obviously much less well-known, but is also much smaller.
Edit : just realised, the airport city Roissy-en-France at under 3k inhabitants is a huge contender too that wasn’t mentioned
Admittedly my WW2 history knowledge is quite lacking, but I don’t recognise Vichy because of the war stuff.
But I do recognise Vichy! Because we have a sub-type of mineral water in Sweden that is named after Vichy, “Vichyvatten”. Wikipedia tells me the original was from a spring near Vichy, hence the name.
Also consider that Roquefort-sur-Soulzon, of cheese fame, has 528 inhabitants.