Yes, you still need to file with the IRS, especially if you have income that is effectively connected with a US trade or business. This income should be reported on Form 1040-NR, US Nonresident Alien Income Tax Return. Fixed, determinable, annual, or periodic (FDAP) income that is not effectively connected with a US trade or business is taxed at a flat 30 percent rate (or a lower treaty rate if you qualify) and no deductions are allowed against such income. FDAP income includes dividends, interest, and other types of income from US investments and must be reported on Form 1040-NR if it is not effectively connected with a US trade or business​

The cost for a US citizen to expatriate, which includes renouncing US citizenship, involves paying a fee of $2,350. Additionally, certain expatriates, classified as "covered expatriates," may be subject to an expatriation tax or exit tax​. The expatriation or exit tax is a form of taxation that applies to individuals who renounce their US citizenship or long-term residents who give up their green card. This tax is assessed on the net unrealized gain of the individual's property as if the property had been sold for its fair market value on the day before the expatriation date. Essentially, it's treated as a capital gains tax, capturing the built-up value in the expatriate's assets.

If you didn't know you were subject to file US tax returns, you should consider taking advantage of the IRS Streamlined Filing Compliance Procedures. This amnesty program is designed to allow people who were unaware of their filing requirements to come forward without facing penalties and get up to date on their expat taxes. The program requires you to file your most recent 3 years of late tax returns and 6 years of FBAR, alongside Form 14653, Certification by US Person Residing Outside of the US