Connections of <30 minutes are common at US airports - which are perfectly doable especially when your plane you get off is the same one as your next flight. (Somewhat better than LH who park the plane off gate at FRA, bus you all the way to the other end of the terminal, get you to walk the length of the terminal to get on another bus to get on the same plane for your forward connection).
Meanwhile, exactly 4 weeks ago, my cancelled BWI-LHR and rebooked IAD-LHR reduced my 3h15 connection to 75 mins (T5-T5) - which I made, just. Today's BWI-LHR cancelled/rebooking IAD-LHR with connection (T5-T3) reduced from 4 hours to 2 hours - oh no, you can't possibly do that, so they rebook my connecting flight to give me a 5 hour connection. Doh.