FDR would have been in quite a pickle if Hitler had sent condolences to the USA and broken his alliance with Japan instead. (After all, he was getting exactly zero benefit from the alliance.) The American war plan was Germany First, period. There was no real plan B. A concillatory gesture from Hitler on Dec 7th would at the least have cost the Western Allies months of delay and thrown war preparations into chaos.
The US would have sent a ship into the Atlantic just begging the Germans to fire on it, in order to give them a Casus Belli.