Thanks for the response above. I really hope those who have such a experience could answer my question.
In fact, I once drove from US to Canada and drove back to US with B1 single-trip visa without any problem. But I'm not sure what will happen if someone takes flight. Thanks.
Question about B1/B2 visa. If a Chinese holding B1/B2 SINGLE-trip US visa wants to visit Canada from US, will he be allowed to re-enter US again with this B1/B2 SINGLE-trip visa? Thanks in advance for your answer.