Originally Posted by MBAustin
I hope some of our multinational members can be helpful. However, many of your questions are quite specific to your relatively uncommon situation and, as they could have significant implications for your financial future, I suggest that you seek out a financial professional (CPA perhaps) with relevant experience.
Good luck with your journey to ER wherever it takes you!
I have been in exactly the opposite situation, so I cannot answer your questions as such but I can give you something to think about.
As I understand it, many (most?) countries do not recognize US tax protected programs such as Roths and before-tax IRAs and 401ks. Income and gains in them will probably be taxed in your country, so why leave them here?
If you leave any income-producing assets in the US, you will have to file for taxes in the US AND your country. This requires expensive expert help.
Consider simplifying your future situation by cashing out here. You ought to be able to invest in the US economy at home.
If you are worried about exit taxes, you have a lot of money. Consider remaining here as a permanent resident for a calendar year after you quit, living off your assets. A low income tax year may be helpful.
Be wary of becoming a US citizen. It follows you everywhere. A permanent resident (green card) can stay here. I know English, Danes and Dutch who have worked here and retired here without becoming US citizens. Incidentally, I don't think the US bothers about dual citizenship anymore unless you go and serve in a foreign army.
You should know that you have to work 40 quarters (10 years) putting into Social Security before you qualify to receive SS benefits. If you don't work here that long, it was just another tax. You can receive SS benefits even if you live in most countries.
Your current employer probably retains an international tax consultant (they may need to, because you are on their payroll). Start there. Pay them yourself if you have to. You need expert advice.