Yes, your ESTA is valid for up to 90 days. However, it's still up to the immigration officer to determine (at any time) whether or not you should be allowed back in to the country. So problems - not because of your ESTA, I did what you're describing back in July (went from the US (1 week) to Cuba, Canada and then back into the US 2 weeks later), and had no issues. A week later I returned to Canada for 2 days, and then went back to Seattle to fly out. So basically what you're describing!

Of course, they may have the usual questions about your departure flights, accommodation etc that you might get on your first arrival too, but as long as you have those sorted, you should be fine.

Yes, your ESTA is valid for up to two years, and you can spend up to 90 days at a time in the country. However, it's still up to the immigration officer to determine (at any time) whether or not you should be allowed back in to the country. So problems - not because of your ESTA, I did what you're describing back in July (went from the US (1 week) to Cuba, Canada and then back into the US 2 weeks later), and had no issues. A week later I returned to Canada for 2 days, and then went back to Seattle to fly out. So basically what you're describing!

Of course, they may have the usual questions about your departure flights, accommodation etc that you might get on your first arrival too, but as long as you have those sorted, you should be fine.