.
Both Boeing and Embraer have no airliner that can compete effectively with the Bombardier CSeries. And so with Airbus for that matter except for its proposed but bigger A-320NEO.
Airbus is wooing the Chinese effectively with their A-320 production in China, and so is with Bombardier with its sourcing of the CSeries' fuselage from China.
Boeing may do better by cooperating with Embraer in a new 130 seater 737NG Replacement to compete directly with the Bombardier CSeries. Through this, Boeing can leverage the technology, production and market of Brazil and Latin America.
Boeing can even up the ante by the participation of the Indian aerospace industry and getting an edge in the fast growing Indian airliner sector. Boeing have already a wide and very good relationship with the Japanese aerospace industry, and with the Russian aerospace industry in the DreamLifter 747 conversion.
Why a 130 seater?
1. To compete effectively with the Bombardier CSeries and cover the area where Airbus is weak.
2. Embraer has no exact model in this capacity.
3. Take advantage of the DC-9/MD-80 replacement cycle.
4. Keep open the option of re-engining the larger 737-800/900 series to cover the 757 replacement cycle.
5. As a B-717 replacement.
Just remember the B-737 started off as a 130 seater in the 1960's and it has grown effectively to a 200 seater and more airliner.
To do this cooperation, Boeing has to effectively woo Embraer as it has had closer historical relationships with the Europeans.