Even you have the most efficient airliner built with lowest operting cost but no control market or political influence. You are game over.

Russia super sukhoi 100 is quite a decent modern regional airliner and yet how many are sold? If you bother to check, most of the sales are thru Russia domestic airliner. But Russian domestic airliner are weak and cannot afford a huge order.

China ARJ-21 in fact is quite an outdated airliner(non fuel efficient) with unproven maufacturer despite not debut yet. Who in the right mind will buy it? Yet it secures more than 300 over hundreds. All thru political string for foreign sales or order from stated for domestic airliners. ARJ-21 is just an interim solution until the bigger and more efficient C919 enter service. Domestic state airliner will definitely order by CPC to buy certain number of C919.

Regarding FAA or EAA cert. It is not a must for C919 to attain first since they will definitely make things difficult for C919 to attain such process to go global. Most important is to satisfy domestic China demand as China aviation market will be the most lucrative and important for the next 20 years. Boeing estimate China need 6200 plane  and imagine China C919 can just capture than 1000 plane market out of 6200 need. How much revenue can it generate or prevent it from slipping into Boeing and Airbus hand?