Upvote:2
In theory it is possible! I spent exactly 90 days in the US with a ESTA visa waiver (also coming from South America), then I traveled for about 3 weeks in Canada and entered the US with a flight ticket that left 2 weeks later from NYC - there was no problem at all coming back into the country, just make sure you have your tickets ready to show at the border crossing. Canada and the US are NOT considered as one country by the US immigration. Of course, it is always up to the officer in charge to let you in or not, but as I said, I didn't have any problems at all.
Upvote:4
The government documentation covers your explicit scenario. You can come back in if the CBP officer believes you are not just trying to reset your visa. Having a flight booked for one day's time should be sufficient.
If you go to Canada and Mexico or the Caribbean, and while you are there, your initial 90-day period of entry expires, but you need to come back in to the U.S. to fly home, you may encounter a problem. The terms of the VWP are very clear - it is only to be used for occasional, short visits to the U.S. If the CBP Officer thinks you are trying to "reset" the clock by making a short trip out of the U.S. and re-entering for another 90-day period, you can be denied entry. (If that happens, you will have to obtain a visa for any future travel to the U.S.) In order to be re-admitted to the U.S. shortly after a previous admission expired, you will have to convince a CBP Officer that you are not trying to "game" the system.