I don't think there is any chance of the NDP winning th […]
I don't think there is any chance of the NDP winning the October, 2019 federal election. In fact, unless they become a very different party, I doubt they can win any federal election. However this is too interesting of a question to pass on. It causes us to think about a few aspects of Canada's relations with the USA.
As another Answer pointed out, the NDP, unless currently, isn't a far left party. However, how well that would be understood in the USA is another question. The American electorate hasn't shown that much sophistication in differentiating between mild social democracy and outright authoritarian socialism.
Since the next federal election is next year, presumablyFruit Squeezing Belts Suppliers the current American administration would be dealing with such an event. (Unless of course things like impeachment or onset dementia interfere.) We do not of course know what the composition of the next Congress will be. The United States Senate and the House of Representatives are not as strict in party discipline as our Parliament. I suspect it would have more to do with the attitude and concerns of individual members of the two houses of Congress, rather than a Republican or Democratic Party line.
What Happens When Canada Crosses The American Consciousness Threshold?
I contend that the threshold for general American consciousness about anything in Canada is rather high. There is a distinct tendency to see Canada as something not worth seeing. Since Canada is seen as non-threatening and unimportant, and not different in any substantial way from the USA, why would it need attention?
However, that is the general American attitude. The business community in particular, has corporate executives who are very interested in Canada. These are the companies that have branch operations in Canada and that trade with Canada. They are also companies that tend to be politically quite influential. This could either moderate or exacerbate any American response. If the corporate executives are knowledgeable enough about Canadian politics to understand that the NDP is a rhetoric-oriented party, they might suggest that no special American response is required, unless the NDP federal government does something bad. However, if these are executives who are not informed about Canada, or hate what they see, they may do their very best to convey their alarm to the White House.
The current White House has some individual actors who themselves might have a very low threshold for Canada doing or being anything that they don't like. Imagine how Larry Kudlow would respond to the new Jagmeet Singh government! (Presuming he is still party leader.) Sadly, they might take even the turban as a sort of foreign slap against the Trump administration.