Basically, my contention was that Americans are suspicious, if not outright scared, of strangers, and that Europeans aren't.
Dorfy wrote that you cannot generalize because "our country is so large and so varied." I have said similar things many times, and there undoubtedly is a kernel of truth to it: generalizations, by definition, always miss the mark. In turn, there is a sliver of truth to caricatures, and that is what makes them effective.
On the other hand, the United States is actually incredibly homogenous given its size, so I would actually argue that culturally, linguistically, etc. there is more variation in relatively tiny Great Britain than in the US.
The same could be said for other European countries. Take Spain, which currently has at least three regions (Basque, Catalonia, and Galicia) that seem to want their independence. The German spoken in Bavaria, Switzerland, and northern Germany is mutually unintelligible (much more than simple things like you wont yo' po'boy dressed?); you can't get Bavarian Weißwürste here in Freiburg at all to my knowledge, and the northern Germans eat things like herring for breakfast, which I have not seen here in the south yet.
All of these national differences take place within an area roughly the size of Mississippi.
But back to my other contentions. The movie Crash was received over here as an example of how car culture actually isolates people, and we only get to know each other we get out of our cars -- which was held to be true both in Europe and the US, though car culture is more widespread in the US.
As chance would have it, the New Yorker has just published this review of a series of photographs taken by a Frenchman in the 50s, and the picture of a lunch counter at a drugstore (shown on the website) provokes the following comment:
Every stool is taken; the customers are waiting for their orders, two of them clasping their hands as if saying grace. Half of them look straight ahead, like drivers in dense traffic; not one seems to be talking to his neighbors... this broken togetherness would have been bewildering to one who grew up amid the café society of Europe, with its binding hubbub.
I am reminded of Edward Hopper's Nighthawks, though that painting admittedly depicts the mood right after Pearl Harbor.
Amsterdam famously has apartments with very large windows directly at street level. The most surprising thing, however, is that the residents do not put up curtains and close themselves off, but rather seem to want to put their living rooms on display -- as though to say, I have nothing to hide, and I bet your living room doesn't have such lovely wood paneling. (Read this.) Amsterdam practically invites passersby to peep in.
So when it comes to a fear of strangers, Europe simply cannot compete with the US. We are not afraid over here in the old world. In the US, I have been accosted several times by beggars, who were downright aggressive and seemed to be threatening me with violence if I didn't give them something. In Germany and France, you tell punks on the street that you are not donating, and they wish you a nice day -- I kid you not.
Having said that, a few years ago I wrote about how Americans are much more open to meeting new people in all situations, whereas you mainly meet new people in Europe through your existing friends. Returning to the photograph from 1955 mentioned above, in the US you can walk into a greasy spoon and sit at the bar, and there is a chance that your neighbor will talk to you. But Europeans don't have greasy spoons and instead go to cafés with their friends. I guess if you don't have any, you're just not going to make any, which explains why Americans are much more open to mobility than Europeans are.
Interestingly, the author of that New Yorker article does not buy the interpretation that the Americans at the drugstore lunch bar will not speak to each other:
Maybe they just came off a noisy shift, and could use a minute’s peace; maybe they’re simply tired and hungry; maybe, with a grilled-cheese sandwich and a cup of coffee inside them, they might warm up, and, if the man with the camera returned in half an hour, he would walk into a perfect storm of yakking.
I agree. And while Jean-Paul Sartre et al. may have met new people in cafés 70 years ago, it is certainly rare today in Germany and France to talk to anyone you don't know in a café.
So Americans are, I suppose, always open to making new friends -- but they also carry a lot of suspicion with them; in contrast, Europeans may be a tough nut to crack, but not because they think you're a creep.