I've been back and forth across the border thousands of times. It's kind of funny... if you're white, doesn't matter what you look like, you can get through. If you're not white, it is substantially harder, even if you have no other reason to be suspected of anything. This goes for customs on both sides. I've seen them let the shadiest white guys through without much hassle, and I've seen them detain black guys for hours, tearing apart their car doing thousands of dollars in damage only to find nothing.