Why is the IRS coming after me I'm not a US citizen nor have I been to the US?

I work in Canada, pay Canadian taxes and only do business and shop in Canada.

Should I just start ignoring the IRS? I'm beginning to think it's a scam.
Update: @Anonymous, it came through the mail. My family; parents, grandparents on both sides of my family are Canadian and never worked in the US. All family are Canadian born and we all worked and did business in Canada. Why would I the only member of my family receive an IRS notice in the post?
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