To compare our experience with stopping in North America, as opposed to going to Europe non-stop, last summer we flew SFO-Toronto-Copenhagen. It was an award flight, so our choices were limited. We had a 7am flight out of SFO, meaning a very early get up to leave for the airport. This was with a planned 4 hour layover in Toronto. Originally scheduled to arrive in Copenhagen about 10am local time.
However, our Toronto to Copenhagen left and arrived over 3 hours late. It is only a 6 or so hour flight, so with dinner and breakfast, there wasn't even 4 hours for attempts at sleep. Conversely, the SFO-MUC flight is close to 11 hours, so much more time to attempt sleep, which, at least for me, isn't too hard on a plane. That extra sleep really helps with time zone changes.
That is a key part of the reasoning behind going non-stop to, and connecting in, Europe.