The close relationship between Canada and the United States is difficult to quantify and goes far beyond sharing the longest unguarded border in the world. They are each other's respective biggest trading partners as well as heavily influencing their respective cultures. Beyond that, people from each country are also frequent tourists across that unguarded border in both directions. It's usually a mostly amicable relationship. Usually.
With Donald Trump inaugurated as the next President of the United States, that signals a shift in the relationship. Trump has already made polarizing comments about Canada which haven't sat well with either the political right or left. Average Canadians are also concerned about how Trump will run the United States since it can be hard to tell the difference between his bluster and his actual intentions.
A recent study by Narrative Research has shown that 30% of Canadians are planning fewer trips to the US because of Trump's next term in office. Those numbers actually increase depending on region of Canada is responding. In particular, Canadian women have indicated that they feel less safe traveling in the US while Trump is President. His past comments about women and his political stances are huge contributing factors to these sentiments.
At the same time, Trump's government cannot be totally blamed for Canadian travel plans. The USD currently has $0.30 on the CAD, meaning it is also 30% more expensive for Canadians to travel to the United States. Having to pay an extra 30 cents on the dollar to plan a vacation will absolutely curtail many unnecessary travel plans. Combining the added costs with concerns about a Trump government will certainly cause many Canadians to look elsewhere when planning their upcoming getaways.