Well… there is also Eritrea, a small country in West Africa.
The U. S. Taxes is based on the country you’re living in. If there are double taxation treaties between the two countries (ie: Europe and the U. S.), then the IRS would tax you on the amount you’ve earned over a certain limit (it was 100k usd, but I think was increased). Meaning, if you earned 110k usd, you’d be taxes on the 10k. If you earn less then 100k, you’d pay no U. S. Taxes.
If there isn’t a treaty, which is often the case in countries that tax their citizens less than the U. S. , then you’d basically be charged taxes in the U. S. (based on your worldwide income) minus whatever you paid the country you’re living in.
One of your questions I didn’t see answered:
You have two choices:
Full Disclosure : you tell the IRS, you haven’t filled and ask them to help you rectify the situation. This could mean penalties and fines for filing late or based on your situation, they might let is slide (as it was an honest oversight). Once you’ve gone through this, then your back in the IRS’ good graces (assuming you still file your taxes and fbar annually)
A “stealth” disclosure : (there’s a better name but I forgot was it’s called) basically, you just start to file your 2023 taxes and pretend that nothing has happened during the last 18 years… if you do this for the next 5 years (or 7 years?) and the IRS does not say anything, then you’re back in the IRS good graces (they can only penalize you for x number of years) . But if the IRS decides to contact you, then they could throw the book at you (more than if you went with option 1).
Ultimately, it’s a gamble with a risk. However, if you’ve recently learned of your citizenship and got a passport. I think it’s quite plausible to get some lienency, both for the full disclosure and the stealth disclosure.