Shipping a bus from the US

In addition to the transportation costs, you may need to consider alteration costs to retrofit the vehicle  to Italy 's different emission/other vehicle standards. I wanted to bring over my BMW(US model) and , after a internet research , I found out it could cost me over $5k to retrofit to their standards. Buona fortuna

I assume you are asking about importing an RV in order to roam around the country without paying expensive hotel bills? Frankly forget it as per the previous answer there are huge taxes on importing vehicles as the customs assume you are trying to make a fast buck selling the vehicle here, also should you breakdown where would you get parts? Plus those enormous machines take some filling, currently 1 ltr is 1.52 euros x 4.6 to get 1 USA gallon and scream.
If you want to drive about and live in your vehicle why not rent a 'camper-van' it is a very popular thing to do and many European visitors to Italy and others do this each summer, though not this year of course.
If you do decide to look into this get your rental and insurance on-line prior to arrival as insurance is very very expensive here 3rd party for an over 40 year experienced diver with no points or claims on a tiny car costs over 300 euros per year for 3rd party only, fully comprehensive insurance is not used here and the driver is not insured unless specified! Plus the rental costs are hugely more in the airports and offices.
I Don't want to stop your ambitions but a rethink might be in order, trains are very cheap and there are mega buses that do top to toe Europe destinations that are extremely cheap, have a look at 'themaninseat51' website, it might give you some ideas.
Ciao
Marguerite