I am flying to Italy from the U.S. My itinerary consists of 2 stops, one in America and one in Europe prior to arriving in Italy. I know it is recommended that I arrive at the airport 3 hours early for international flights, but is this still the case if my first flight is not directly international and is technically a domestic flight?

Say this is the itinerary, for example, in case you need clarification: Denver to JFK, JFK to Frankfurt, Frankfurt to Venice. Technically Denver to JFK is domestic, so does this recommendation only apply if you were flying directly to a different country?