Vasil writes, "I have been a US citizen for over a decade but have decided to return to my native country. I am also hoping that I will marry there and spend the rest of my life there. The woman I am likely to marry has no intention of coming to the US or living here permanently. What are my responsibilities as a US citizen after I get married?"
There is no specific requirement to report your marriage as such, but after marrying, you will be bound by law to report if you are filing your tax return as single or married (by law if you are a US citizen, regardless of where you live or work, you will need to file a tax return in the US on your worldwide income, even if you plan to never return to America). At that point you will need to update the IRS and Social Security Administration (SSA) records and that is why it is a good idea to get her an individual tax identification number (ITIN) that she can use to file her return and for this she never has to set foot in the US. Not only is this the law (while the IRS may not come after you, if your income is small, but will surely do so if your income is huge, and if you do not file your returns and ever try to return to the US, you will be definitely arrested at the airport and prosecuted for tax evasion), you and your wife will be eligible for all the benefits that the United States government provides in retirement and/or during disability. If for some reason, you and/or your wife really do not care about the US, after paying all your taxes and debts, you should surrender your American citizenship so that you will no longer be bound by American laws. You will, however, forfeit all your Social Security payments for which you made a contribution while you were working.