But sure, it's all because of Trudeau's ego.
"beginning in early January 2022, DHS will require that all inbound foreign national travelers crossing U.S. land or ferry POEs – whether for essential or non-essential reasons – be fully vaccinated for COVID-19 and provide related proof of vaccination. This approach will provide ample time for essential travelers such as truckers, students, and healthcare workers to get vaccinated."
https://www.dhs.gov/news/2021/10/12/secretary-mayorkas-allow...