Of course teams should have been headed for Frankfurt to catch the nonstop flight to Portland OR. There is no nonstop flight from Munich to Portland. If a team mistakenly went from Moscow to Munich, they would not be able to catch up with LH468 out of Frankfurt. The standard alternative for them to reach Portland OR is:
Air Berlin 6026 Departs: 9:55a from MUC Arrives: 11:10a Düsseldorf (DUS)
[ Layover in Dusseldorf, Germany (DUS) for 1h 50m ]
LTU International 1582 Departs: 1:00p from DUS Arrives: 2:05p Vancouver Intl (YVR)
[ Layover in Vancouver, BC, Canada (YVR) for 2h 45m ]
United 8225 Departs: 4:50p YVR Arrives: 6:05p Portland (PDX)
Your route through Chicago-O'Hare is even better, as it gets them in 12 minutes earlier(if on time):
LH434 dep. MUC 0900 arr. ORD 1140
UA 929 dep. ORD 1530 arr. PDX 1753
It is possible that a travel agent screwed it up for whichever team is affected and booked them flights to the wrong Portland.
There are no nonstop flights from Munich to Boston arriving before the evening. There is one from Frankfurt:
LH422 dep. FRA 1225 arr. BOS 1430
At this point it would be easier to rent a car and drive 2 1/4 hours to Portland ME, but Amazing Race rules do not allow it unless a team is getting a Guido exit. Flying from Boston to Portland is one of those "you can't get there form here" situations as there are no nonstops in the right time frame. Leaving after 3pm there is no combination of flights that gets anyone to Portland ME until 11pm at the earliest.
If a team made the mistake and discovered it in Boston airport, then there is a nonstop Alaska Airlines 31 dep. BOS 1635 arr. PDX 2005.