Yet still Boeing flexed their lobbyists.
[1]https://en.wikipedia.org/wiki/CSeries_dumping_petition_by_Bo...
Boeing's bid to Delta was some Embraer E series they had from an Air Canada trade-in. [1]
No model of 737MAX competes with the C Series for Delta's RFP. Both Boeing and Delta have readily admitted this when asked (see [1]).
Boeing has nothing in the market to compete with regional jets like the C Series. This is exactly why they are now looking into buying Embraer to counter Airbus acquiring a majority stake in the C Series. [2]
[1] https://www.forbes.com/sites/scotthamilton5/2016/05/17/embra...
[2] https://www.bloomberg.com/news/articles/2017-12-21/boeing-is...
So to bid against Bombardier, Boeing didn't even try to offer 737s, knowing they can't fit Delta's needs. Instead they offered 717s and Embrauers, both of which are used (Boeing canceled the 717 over a decade ago).
Foreign automakers can't sell trucks in the US.