If I buy an iPhone 5 in USA, can I use it in Italy?!

IF you buy an unlocked iphone directly from Apple.

The warranty will not be valid in Italy.

There will be no choice of model.

If you have problems with the iphone, you will not be able to get service in Italy. You will have to get the iphone back to the U.S, then to Apple.

The only officially unlocked iPhone 5 model, sold in the US, is the A1428 GSM model. Not only will your warranty support only be valid in the US, but the phone will not support LTE anywhere other than North America.

Doubt you'll save much, if any, money by the time you pay tax & duty fees. Seems like a poor idea to me.

You're welcome.

FYI:

You purchase an iPhone in any EU country & your warranty/support is EU wide. Not to mention, your warranty is two years, if purchased in Italy, vs one year if purchased in the US.