Us Domestic auto insurance does not generally cover overseas cars. Your credit card does carry the C

Us Domestic auto insurance does not generally cover overseas cars. Your credit card does carry the CDW except in certain countries including Italy. When you rent a car in Italy, you will be fully insured minus a deductible. Some companies claim to rent with no deductible, but that does not include damage to tires and glass.
Your domestic france river tour cruise loire auto insurance is HIGHLY unlikely to cover you anywhere in Europe, but your credit card might, with certain limitations. You can also, if you're an AMEX card holder, sign up for their special insurance packet for overseas rentals france river tour cruise loire (I think it's about $25 a trip), which may or may not cover everything in Italy (which has more stringent insurance requirements than other countries).
Many american credit cards provide coverage for rental cars outside the US. but usually with a deductible andt hey typically do not cover either Italy (due to theft) or Ireland france river tour cruise loire (due to the number of accidents). But do check with you credit cards - it may vary (visa regular is a far cry from AmEx black).
However, I believe that the rental agencies in Italy require that you take their insurance - so you may not have any choice. Be sure that any price you are quoted is inclusive of both VAT (sales tax) and insurance.
You do not want a car in Rome or Naples. Many Italian cities have restricted zones (ZTL) and you are not allowed to drive in those areas unless you have a permit (resident, business, etc.). These areas are controlled france river tour cruise loire by cameras that snap your license plate so they can mail you a ticket.
Naples has some of the craziest drivers in Italy and most cars you see are dented. You would have to pay 35-45 per night to park a car overnight in a parking facility in either city. Many hotels will not have parking and will direct you to the parking garages.
If coming to this part of the world, you might ask specifically re ferrying the car over to the various islands - as and where allowed! Could well be an extra cost, to cope with recovery if there's a problem.
But even if deciding to avoid their centres, you may well want to use the car elsewhere in the provinces of Rome (2000 sq miles) and Naples... within whose 450 sq miles there's Pompei, the Sorrento side of the AC peninsula and - of course - Ischia!