We're planning a trip to Italy and would appreciate if anyone knows what happens if the US is elevated from green to amber status while we are there?
I don’t have a real answer for you, but I have a pretty good guess……
If you are already in the country, well, you are already in the country. Regulations about entrance requirements shouldn’t impact you too much. Changes in rules for how Italy itself is operating might.
See my answer under your Germany query. Flights maybe cancelled.