Hi, for your peace of mind, you could print out the final page on this questionnaire on the travel advice website for Italy's Ministry of Foreign Affairs.

https://infocovid.viaggiaresicuri.it/index_en.html

The questionnaire should be updated by March 1 to reflect the new rules, and the final page will show the current entry requirements into Italy, taking into account your departure country (US) and transit country (UK).