Yes, because this affects the timeline of the delivery of C Series aircraft to US airlines.
Airlines who are counting on those aircraft so that they can continue to modernize their fleets and reduce their operating costs accordingly.
This decision is hurting US airlines, and is affecting US jobs. Getting into a measuring contest with Canada, our second largest trading partner, doesn't do any good. Free trade is a cornerstone of a globalized world, and this is stifling what is otherwise fair competition.
I mean Jesus Christ, guys, how did we get to the point that I'm the one giving lectures on free trade and the benefits of global capitalism? Has everyone gone mad?