As a US citizen, you are required to report your income earned worldwide. So yes, you are required to file a return in the US and you would need to report your income from Canada or from any other sources in the world.
Since you permanent reside outside of the US, you would be allowed to claim the foreign earned income exclusion which is currently $91,400 per year. What that means is that the first $91,400 you have in foreign earnings would be exempt from US tax. But even if your income is below this amount, you are still required to file a return and report your income and claim the exemption.
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