All the above is correct. There really is no issue with it. However a piece of advice. Try to exit the US from the same point of entry (i.e. back into Canada) that you entered in to. In theory you can leave from a different point but on occasions when I and colleagues have done this (i.e. for business / connection reasons it has ALMOST ALWAYS caused problems.
But be friendly, and they will be too. They are human - just doin' their job.
PM