How have you been approached? Email? Absolutely a scam. Do NOT reply to email. Do NOT even open any email claiming to come from IRS, or any US govt agency/dept. US & state govts never use email, only letters mailed through US Postal Service.
If you got a letter, inspect it carefully as it could be fake/forgery. CALL the nearest US consulate to your home in Canada & ask for the IRS representative. Tell them you think you are the victim of a fraud claiming to be IRS. Do NOT call any number given in the letter, or respond to the letter directly, as it could be a scam. Another possibility is mistaken identity, but more likely, it's a scam.