1. "Prolly" does not exist as a word
2. FB does not require you to commence journeys from the US - you must be doing something wrong. (Try typing "PRG" in the "To" field).
3. To book a Flying Blue award, you would first have to transfer Amex MR points into your Flying Blue account (making sure to open one first, if you don't already have one)
4. Short-haul flights are an appallingly bad and wasteful use of FB miles (and hence of Amex MR points). You should be aware that the taxes and charges you will be charged in cash for a return ticket are, in most cases, far more than the cheapest revenue fares for the same return ticket (i.e. just buying a normal ticket from
www.czechairlines.com or from
www.klm.com will cost you less cash - and no miles - than making a Flying Blue redemption in short haul). The only usual case where it makes sense to redeem FB miles for short-haul is if the flight is leaving in the next day or two and hence the revenue fares are sky-high, or if you require some degree of flexibility with the booking, or if you are making a one-way booking (as one-ways are quite expensive).
In short - I would advise you to abandon the plan of doing an Amex MR -> Flying Blue FB transfer for these purposes, and to just buy a revenue ticket.