The international terminal is "E", and if you are going to return on USAir, you go to "B" which Goggle claims is a 12 minute walk across the pedestrian bridge.
If I recall, I think that's pretty optimistic after passport control and re-checking baggage. Last time I used Logan, I want to say I gave myself more than 90 minutes to connect using the DL connection to get back to GSO.
Candidly, I avoid CDG--the last time my Italian mates connected through there(February this year), the bus driver from the main terminal to the departure terminal for the U.S.flights just refused to move after he loaded the passengers! Yes, DL did get them on a different flight, they spent most of the day there.