American accents are ubiquitous in UK media. I don't have any strong feelings about them at all. They're not a novelty in any way, shape or form, which is the impression I get sometimes when I hear some Americans gushing about British accents (some of which, let's be honest, can sound pretty unappealing.) They're just another accent.
There is a type of American accent, I think it's mainly from the North Eastern parts of the country, where the tone of the accent is really nasal to a British ear. I don't think that sounds particularly pleasant. But it's no worse than for example the Birmingham or Liverpool accents in Britain. There was an old playground game when I was at school where you had to try and make yourself sound American by pinching the bridge of your nose and pretending you had a mouth 'full of Rs.' Misspent youth.
Maybe you genuinely have an American accent but Italians tend to have quite strong accents in English. People are almost certainly going to think you have an Italian accent, not an American one. There is a difference between learning American English pronunciation and having an American accent.
Two things that worry me
People who insist in putting their hand on their chin or over their mouth when they speak. It doesn't matter what accent you use if it is just a mumble
The use of the rising inflection to mean a question. That just sounds like you are uncertain.
If you avoid those two you'll be fine
Just another thought. Have you noticed that baddies in US movies are either Russians or Brits. Drives me mad, don't you know all baddies are Russian! :-)
It really depends. I quite like the southern accent. It sounds quite melodic.
I really struggle with those really loud screaming "legally blonde" vapid Paris Hilton characters. And when people from the west coast go up at the end of every sentence. That's rather annoying. Oh and the over use of 'like' - but that's not a uniquely American problem.