回複：來美國開會,想去看大瀑布，攜美國簽證，可以去加拿大看嗎？

When you are in US border, nobody bothers you. You are free to leave from US. When you are in Canadian border, a Canadian official definitely checks your documents and he never lets you enter Canada without Canadian vise if you hold Chinese passport. He issues a letter to you and then you have to come back to US border with the letter. A official in US border checks your documents and normally he permits you to reenter US. Every day, a lot people make the mistake, so you have to wait for the document check from a US official for almost half of a day.