This is entirely UA's problem until the day of departure when you check-in with the foreign carrier.
You can call UA and ask them to check the flight times. If they realize you violate the MCT rules you might be able to convince them to get you on the earlier flight. The problem here is UA has no control over award space on the other airlines and if there is no award space UA can't magically open it up for you. So your option there would be to take UA-operated flights to your connection point in Europe or wherever it is and then keep your onward connection on the foreign carrier.
Tell us which airport you are connecting through and we can offer opinions on whether 55 minutes is doable. For example, 55 minutes in FRA is more than enough.
Are both flights operated by the same foreign carrier?
-RM