Not sure where people discussing this as a US vs CA or that this is somehow a win are getting those ideas from.
No one gets upset when agricultural products (many of them, frankly, more high tech than these things) get caught up in similar trade disputes, which happens regularly too.
I can't help but think this is driven in large part by a perception of this as a US assault on Canadian innovation, when it's really just another corn war.
Most of those are now out of production or nearing the end of their production run, which is why new, cheaper to operate designs for this category are being developed (Embraer and Mitsubishi are also developing new regional jets).
The funny thing is that Boeing doesn't even have a competing product in this market!
Boeing underestimated Airbus in the 70s and 80s, and they’re trying not to make the same mistake again. They were trying to head this off before it gets that far.
It was also a huge issue in the UK as Bombardier is the largest private sector employer in Northern Ireland which is politically critical to the current UK Conservative government as they are a minority and depend on support from one of the unionist NI parties to function.
I'm sure the UK government desperately wanted a solution to this crisis - having a government collapse in the middle of Brexit negotiations would have been a disaster.
That's the kind of market Bombardier was aiming at. And it's a bad bet, protectionism or no. It's very likely this plane would have failed regardless.