WILLIAM BRANGHAM: More Canadians come to America than tourists from any other country.

Last year, Canadians made over 20 million visits to the U.S. and spent more than $20 billion here.

But, this year, many are not coming to America, as I saw firsthand on a recent trip to Vermont right near the Canadian border.

In a normal summer, the Kingdom Trails in Vermont's Northeast kingdom near the Quebec border would be teeming with Canadian bikers.

But executive director Abby Long says this season has been a rough ride.

ABBY LONG, Executive Director, Kingdom Trails: We have seen that 50 percent decline in our Canadian members.

WILLIAM BRANGHAM: Twenty-five miles away, at Hill Farmstead Brewery, business is off by a third.

BOB MONTGOMERY, Hill Farmstead Brewery: We just had a large festival last weekend and 50 or 60 of the ticket holders just did not come.

WILLIAM BRANGHAM: Last year, 20 million Canadians visited the U.S. That's over a quarter of all the tourists who come here.

But in June, car crossings to America dropped by 33 percent.

That's the sixth consecutive month of decline.

Air travel has also plummeted.

So why are Canadians staying away?

DONALD TRUMP, President of the United States: Frankly, Canada should be the 51st state.

WILLIAM BRANGHAM: Most offensive to northern neighbors like Julie Morrison has been President Trump's rhetoric.

JULIE MORRISON, Canadian Tourist: This threat of annexation by this very powerful militarized ally, we took it very, very seriously.

And, honestly, it's frightening.

WILLIAM BRANGHAM: Morrison has happy memories of her many American vacations, but now she's staying home.

JULIE MORRISON: We don't have a lot of tools.

And, well, tourism is one of the tools that we have.

HAROLD WHITE, Canadian Tourist: I feel that I have been slapped across the face by this president.

WILLIAM BRANGHAM: Quebecer Harold White has vacationed in Maine for the last six decades.

This year, he canceled his annual trip.

HAROLD WHITE: And I have many U.S. friends, American friends that I will not be seeing in person for a while because of this.

But that's c'est la vie, as we say here in Quebec.

WILLIAM BRANGHAM: Jay Peak is a mountain resort just a few miles south of the border.

In wintertime, typically, half their seasoned pass holders are Canadian, most of them French speaking Quebecois.

That's clear even in summertime.

STEVE WRIGHT, President and General Manager, Jay Peak Resort: The signage that we have here is mostly all bilingual.

WILLIAM BRANGHAM: General manager Steve Wright has proof... STEVE WRIGHT: I have the maple leaf here.

WILLIAM BRANGHAM: ... that the bonds here run deep.

STEVE WRIGHT: My dad is Canadian.

WILLIAM BRANGHAM: Literally in your blood.

STEVE WRIGHT: Big connection, not just the dollars and the cents, but the DNA.

WILLIAM BRANGHAM: Even so, as the ski season wound down here and it came time to renew, many longtime Canadian season pass holders said no.

STEVE WRIGHT: We are 30 to 35 percent off.

WILLIAM BRANGHAM: And you're sure that this is overall their antipathy to what's coming out of the White House?

STEVE WRIGHT: Well, yes, as much as I guess you can be sure of anything.

I called 100 households myself, Canadian households who had purchased season passes last year by this point who have not yet purchased.

WILLIAM BRANGHAM: You called them directly?

STEVE WRIGHT: I called them directly, personally.

I got through to probably 70 percent of them.

And to a household, they referred back to the 51st state narrative as being emblematic of the reason that they're not coming.

WILLIAM BRANGHAM: Other areas of the resort have also been hit.

STEVE WRIGHT: We have already seen 30 percent of our Canadian golf groups cancel.

We do 42 weeks worth of hockey tournaments.

We're expecting that business to be off upwards of 40 percent by the end of the year.

WILLIAM BRANGHAM: Tourism across this northern part of Vermont is dependent on Canadians, yet they are nowhere to be found.

Normally, the Vermont highways in summertime are full of cars with Canadian license plates.

Here we are in summer on the road We haven't seen any.

Their absence affects even non-tourism businesses.

ABBY LONG: What's devastating is, when they come, there's an economic impact to our community.

Towns will benefit positively.

WILLIAM BRANGHAM: Sure, because they eat and shop and sleep and... ABBY LONG: Gallons of maple syrup.

(LAUGHTER) WILLIAM BRANGHAM: At Hill Farmstead Brewery, the Canadian beer enthusiasts who have come this year have spent less.

BOB MONTGOMERY: The tariff situation means that someone buying beer from us just coming for the day, they will pay not just the provincial tax, but they will now pay a 25 percent additional tariff.

They're paying 43 percent above cost to bring beer back.

WILLIAM BRANGHAM: Wow.

Wow.

BOB MONTGOMERY: And that... WILLIAM BRANGHAM: I mean, your beer is delicious, but, I'm sorry, that might be a real deterrent.

BOB MONTGOMERY: I appreciate it.

It is a real deterrent.

WILLIAM BRANGHAM: And it's not just Americans who are feeling the pinch.

Just steps across the U.S.-Canada border in Quebec, Philippe Bachand's duty-free shop should be bustling this time of year.

PHILIPPE BACHAND, President, Philipsburg Duty Free: But, right now, it's very disappointing.

WILLIAM BRANGHAM: Bachand says Canadian business is down close to 50 percent.

For now, he's squeaking by.

PHILIPPE BACHAND: We did not lay off anybody, but it's -- we need to be careful in ordering and all that.

WILLIAM BRANGHAM: But smaller duty-free shops along the border are on the brink.

PHILIPPE BACHAND: Four to six store are planning to -- if it's going on, they will close by the end -- by fall.

WILLIAM BRANGHAM: To close for good?

PHILIPPE BACHAND: Yes, yes, after 30, 40 years of existing.

We're here on the border with our little white flag, and it's not because of bad management that we're in this situation.

It's because of politics.

WILLIAM BRANGHAM: In Burlington, Vermont, outdoor store owner Mike Donahue (ph) says they're doing what they can to entice their northern neighbors to return.

MIKE DONAHUE, Business Owner: Church Street, which is the pedestrian market, is being renamed through Canada or Canada Street to show our solidarity with our Canadian neighbors.

WILLIAM BRANGHAM: At Kingdom Trails, Abby Long has her own idea.

ABBY LONG: Free mountain bike day, free Canada day, where we shout to the rooftops how much we love them and encourage them to come.

And if they do choose to come, there will be a day in their honor, a free day.

WILLIAM BRANGHAM: Jay Peak offers so-called at-par pricing.

STEVE WRIGHT: We price obviously all of our products in U.S. currency, but we allow Canadians to buy in Canadian currency so they get the benefit of the exchange.

WILLIAM BRANGHAM: But all these efforts may not be enough.

Canadian Harold White is spending his money elsewhere.

HAROLD WHITE: I'm just back from a lovely trip to Spain.

And my wife and I went on a five-hour drive east of Quebec City in the mountains off the St. Lawrence River.

It's a trip that we would not necessarily have done if we had gone to the U.S. for our usual vacation.

WILLIAM BRANGHAM: Canadian Julie Morrison grew up going to Vermont.

JULIE MORRISON: My family has owned property in Vermont all my life.

I learned to ski in Vermont when I was like 3 years old.

We hiked the long trail.

I mean, it's so beautiful.

WILLIAM BRANGHAM: And yet her family has now resolved to sell their home there.

JULIE MORRISON: The process of selling this property for my entire family has been extremely difficult emotionally.

It's almost like we have to mourn this moment.

WILLIAM BRANGHAM: Back at Hill Farmstead Brewery, Bob Montgomery sympathizes with the Canadian boycott.

BOB MONTGOMERY: We actually admire it, to be can... WILLIAM BRANGHAM: Really?

Even though it's got an economic blow to your bottom line.

BOB MONTGOMERY: Yes, absolutely.

Our first outreach is, we completely understand and we look forward to you visiting again when you're ready to visit again.

WILLIAM BRANGHAM: In the meantime, tourist-dependent businesses will just try to ride it out.

For the "PBS News Hour," I'm William Brangham in Northern Vermont.