Hello and thank you for using Just Answer.You as a US citizen should be filing a US tax return. The IRS will normally accept the past 7 years from the citizen that should have been filing but did not. US citizens that live outside the US do not have a free pass on filing tax retruns. US citizens are taxed on worldwide income but they are also allowed to exclude earned income abroad and also to use the foreign tax credit if they are taxed on income in another country. There is alos a tax treaty with countries (Canada included) that determines which country will tax on which type of income. This mainly deals with where the income is earned or sourced.In short, yes you shoudl file a US tax return unless you intend to give up your US citizenship.