Legal Question in Immigration Law in Florida

Your question could be interpreted in two ways. If you are asking how long the US would allow a citizen to be outside the US, the answer is for as long as you want. You could live there for the rest of your life if you want. However, if your question is how lpng will Canada allow a US citizen to stay, that depends on whether you are a visitor, student, worker, applicant for residence and so on. For example, if you are just visiting, you can stay up to 180 days.