Is there a trans atlantic cruise from U.S east coast to italy that allows for a 2 week stay and return trip?

From Italy: no.

Cruise ships navigate the Atlantic Ocean from West to East on spring, and from East to West on fall. You will find most of ships will do this crossing, and some also from Italy. This is "repositioning" and so usually much cheaper. They go on summer on Europe, and in Winter on Caribbean Sea.

There is just Cunard which do regular transatlantic route. Note: technically they ships are not cruise ships but liners: hull and engines are different, for more speed and better transatlantic experience. But they usually depart from England (Southampton), sometime from Ireland or other ports across the Channel (but as far I know, not from Mediterranean).

You may find other cruises which go from North Europe to North US or Canada on regular basis: this is the very new trend, and cruise lines are adding it, but so, you may need to wait 2021 and later.

Cargo ships: this is much more relaxing experience, but often more expensive then the cheaper cabins on normal ships, and you never know exactly the sailing date or the arrival date (and maybe the arrival port could change on last hours).

Note: there are few exceptions, because of dry docks, so sometime cruise ships will cross ocean during spring/summer. This requires a better search in Internet, and you should consider that often such dates varies (according dry-dock availability, which are known much later then the published dates of cruise lines), but it could be a nice option in case of short term planing.