There has been a bunch of chatter in Canadian founders whatsapp groups about people getting detained for long periods of time coming into the states either at SFO or pre-clear in Canada. Are you advising Canadians travel with any additional documentation these days?
There's no question that it's tougher now to get into the U.S., whether from Canada or another country via pre-clearance or via a land crossing, and there can be significant differences among airports and land crossings. Canadians are unique because they are visa exempt and CBP feels particularly emboldened to reassess their admissibility every time they enter. The keys are to avoid bad pre-clearance offices and land crossings and even more importantly to carry the right paperwork, which varies depending on the specific status being sought. There is also a huge difference between seeking entry as a visitor versus seeking entry as a worker with a visa, with the former much more challenging now.
I was thinking just for folks going down regularly on a B1, do you think it's worth having a copy of your lease or rental agreement in Canada or something similar? It seems most of the stuff I was seeing is about Canadians establishing roots using a B1.
The concerns on the part of CBP when someone is seeking admission as a B-1 business visitor are the appropriateness of the applicant's proposed activities and the applicant's ties to home/intent to return home (Canada). So you want to keep in your back pocket documents that address these concerns, such as a foreign lease agreement, foreign pay statement, and evidence of the purpose, such as a printout of the conference being attended or a letter of invitation. It's also really important to be prepared to provide specifics about your purpose, who, what, when, and where.