I am Brazilian and I was in Canada for studies. Since I have a US visa, I came to New York for a few days by car just to visit my cousin. Today I'll head back to Canada by bus and I am wondering what to do with that paper that the American immigration attached to my passport... I mean, I know I have to hand it in when leaving the USA, because that's the only way the American immigration will know that I left before my legal staying limit (6 months).
Since I don't know if the bus will actually make a stop at the border (where I would be able to hand this thing in), I am wondering if I can do this through a Canadian airport. Can I? Because I'm returning to Brazil next week by plane, from Toronto Pearson Airport.
I'm worried that the American immigration might think I overstayed, which would cause me a lot of headache when trying to come back in the future.