回複：求教ImmCanada-

I've been to Canada many times without applying for my H1B stamp at the US consulate. I came back to US within 30 days by using my I-94. Just carry your employment letter, I-797, I-94, pay stubs and other necessary documents. You will need to answer some questions at the border or at the airport in Canada (Yes, the US Customs have offices there).
Don't worry. They will welcome you back. Easy.