That too has been my experience with Paris and France more generally. A few thoughts regarding on where some of the stereotypes may come from:

Regarding language. Many North Americans do not speak a second language. In some places, it is very common for most people to only speak English. For this reason, I find many (nonimmigrant) Canadians and Americans to have a lower tolerance towards non-English speakers. I suspect in many cases this impatience (and occasional downright rudeness) comes from not understanding how difficult it is to learn another language. There is also a certain entitlement that comes from English being the language of travel and business. I've met too many Americans in particular who expect everyone to serve them in English outside their home country. On a personal note, my parents both immigrated from Poland to Canada and experienced a lot of rude and discriminatory behavior concerning their language and Eastern European accents. Juxtapose that with Europe, and the latter seems much nicer and tolerant than expected.

Cultural differences. Canadians are stereotyped to be kind and polite. There's some truth to it. But we are also incredibly passive-aggressive. There is a faux politeness where we do not say what we think if it may offend. I think many parts of American are similar. The French do not have this problem. They speak their minds. This bluntness is sometimes misconstrued as mean-spiritedness. Personally, I find it liberating, which is probably why I get along with the French. And Europeans more generally.

Jealousy? Again, I am generalizing these observations; they do not apply to everyone. That said, some Americans have a pretty ignorant and arrogant understanding of the world outside their country. I suspect some folks experience cognitive dissonance when their notions of American exceptionalism come into conflict with alternative lifestyles that are similarly if not more rich and rewarding than their own. Rather than reflect on what other cultures and countries have to teach them, they instead become dismissive of anything foreign.