Assuming you're trying to maintain AA miles in this process, you might be able to get to KRK via LGW (while avoiding the LHR-LGW transfer) by routing through Bermuda, e.g. JFK-BDA-LGW-KRK; or via Madrid - JFK/ORD/BOS/MIA - MAD - KRK. Not sure any of those are convenient connections, but also don't know your time frame. I assume the MAD-KRK flights (which are in an RJ under Air Nostrum, which is kosher for xONExs) would offer good connections through Barajas.

KRK-PRG could be via MAD also, but you'd quickly run out of European segments by constantly zigzagging through Madrid, Budapest or Gatwick.

Somehow I think there are trains or low cost Euro carriers in your future, however.