I'm a Canadian that have taught at several DL US Universities. There is no need for visa but your options are limited since most schools require a US SIN number to give you a contract. However, DL courses at US schools pay a lot lower than Canadian schools so it is not very attractive for a Canadian to teach online but for the experience (It used to be higher due to the difference in exchange rate). To give you an idea, a local community college at a Canadian school pays around 5 to 7K per courses while an online course pays around 1.5K at it takes about the same effort.
