Two sides of this border crossing in these days have not been covered.
1. Since the assaults on the World Trade Towers, etc. of Sept. 11, 2001, there were "accuse the Canadians, couldn't be Americans fault" types saying that those who made the attacks entered the USA from Canada.
This approach/attitude/blind spot has been disproved again and again and again, but there are still those who won't believe otherwise.
& you know perfectly well Canadian Border Guards have this in the back of their minds during most of their working days. It is something to make them more likely adhere strictly to the regulations.
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2. Partly because the USA has the geography it has and so many US citizens/residents live much more than 100 miles from the border*, there are those who don't understand:
- Canada is a different country. US laws do not apply in Canada.
- US citizens may be special friends to 99% of Canadians, but that's not a part of any law.
- Thus, no special privileges for being a US resident/American ciizen.
......if still puzzled, please google word: "sovereignty".
* Most Canadians live within 100 miles of our joint border. I don't know the numbers.
:C