It's either New Orleans or San Francisco. Boston somewhat but San Francisco and New Orleans have it embedded in their cultures.
i guess the issue to the op is, what does it mean to be "Euro" in terms of a city? Physical characteristics (buildings/houses)? city layout? People/attitudes? Pedestrians? Public transpo? Size/population? Prioritizing different elements leads to different answers. I say no way on Seattle based on how I'm thinking about the question. But all of these can be similar in some ways
Why would anyone say Toronto? When someone says they're form 'America' who assumes that they're talking about Canada? Furthermore, who would ever say that they're from North America? That said, my vote is for Montreal.
Purposefully left the question vague. My first thought was Qubec even though I've never been there and have only been to England/London in Europe. Qubec seems to take great pride in bucking the 'American' image, even speaking French over English.
You guys that say New Orleans, are you referring just to the French Quarter or the actual city itself?
Because, so sorry, there really aren't a lot of U.S. cities that fit the bill. Much like our #1 sport. Just doesn't overall fit the European culture. So you have to look at good public transportation, medium size, well-organized cities. A lot of Europe isn't what you call "clean", but there can be a certain charm nevertheless (not saying I'd trade this country for that country; not saying the idyll is the complete normal, oh no).
I think the monuments, the traffic circles, and the height restrictions are probably the biggest factors that give DC a slight "Euro-feel" in terms of aesthetics.
It's definitely San Francisco. The density, ease of public transit, aesthetics and feel of the city itself are very European.
If we're including North America generally, I'd say more Montreal than Toronto. I'd also introduce Mexico City. The poverty of the suburbs is not very Euro (though European cities tend to have their poverty in the banlieue as well), but the city center feels very European to me. Of US cities, I'd say San Francisco, though I admittedly haven't visited some of the nominations here -- DC, Portland, or Seattle. New York, no. It has the cosmopolitan feel of European capitals, and the density and the subway, but the city doesn't really feel the same at all. I see what people say about Boston particularly in relation to perhaps the non-capital large town in Europe, but I don't feel that very strongly either. I can see what people mean about New Orleans as well, particularly with the French Quarter and the architecture and feel of the oldest parts of town, but too much of New Orleans is not at all like the French Quarter to really count. Outside of the old city, New Orleans feels more like Humble. Even San Francisco though doesn't have as strong a Euro vibe as Montreal or Mexico City -- maybe because those cities are already in foreign countries, they get a leg up.
Apparently, if you do a Google search, there's a lot of mention for Quebec. Never been there myself, so I'll leave y'all to judge that.
None of them is European. But obviously, cities are totally different within Europe. London is different from Moscow. Copenhagen is different from Barcelona. Even within Germany, Berlin and Munich are quite different. But to answer your question - and I have traveled to pretty much every major city in the USA and Europe - it's Boston. It resembles cities along the North Sea in Europe - some British cities and Hamburg. The red brick houses, and so on. Yes, Washington D.C. also a bit. New York City and Miami? Definitely not. Houston and LA - obviously not.
I'd nix Seattle from the list. They're different there -- no doubt, but not so Big City Euro. Too much plaid and gortex. I also don't get the Euro vibe from San Fran. Yes to DC. And if we include 'America' then Montreal by a landslide. Unless we really include 'America' in which case Buenos Aires takes it.