I've travelled to Italy to and have had quite a lengthy discussion on this exact topic with one of my Italian (born and raised Sardinian) friends. I asked him in particular because he is a tour guide in Rome, and so comes across Americans constantly. According to him:
1) American girls are easy. He is in a serious relationship so he didn't do this (he says..) but his friend has had *one night relationships* with many American women. he is also a tour guide. his friend would simply say some sweet nothings with his heavy italian accent and he said the American women would fall for that. He said they constantly commented on both of their accents. He's even hooked up with married women.
2) I won't say all Italians, but he thought Americans were brash, and racist people. His girlfriend (American, living in Rome) is blonde hair and blue eyes and he's Southern Italian, and he said when he visited her back home (small town), they got a lot of looks. He also mentioned that most Italians are ashamed of Italian Americans because they were very racist against black people. He said that he has given tours to some AFrican Americans and they commented how nice the people of Italy were, as compared to their experiences with Italian Americans predominately in NYC.
3) Regarding Italian women, he said that it is difficult for Italian men to pick up (and according to him, Italians are the most passionate Don Juan types... yeah, he's cocky) and so wondered how a rude and crude American can pick them up. I think differently though. I think it is very possible to pick up Italian chicks, i did. But, don't go for stupid cheesy lines because being Italian, they've heard it all before, trust me. And, they are probably SICK of that italian accent so a non italian accent is a good change.
btw, THEY'RE FRIGGIN HOT!
4) Avoid political discussions. Most continental Europeans are really against American foreign policy. He wasn't an exception so i kinda laid off the topic. side note: they HATE our good "ally" the Brits. He was a soccer fiend and mentioned how one time when the British hooligans came over to rome, they started a major fight a few years back, harassed the local women, went bar hopping, and trashed the places and didn't pay... on and on... make sure you make it clear you're NOT A BRIT. btw, if you know a bit of spanish it surprisingly goes a long way. french helps too.
5) Dont' dress "American." Those people are very fashionable, and i felt out of place in my jeans and Tshirts. if you want to dress casual, be stylish casual like Bananna Republic or something.
good luck, Italy is a great country. Good food, drinking, happy people. Much better than most other Europeans.
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