That's only one type of tax treaty. There are also Totalization Agreements. Quoting https://www.irs.gov/Individuals/International-Taxpayers/Totalization-Agreeme

That's only one type of tax treaty. There are also Totalization Agreements. Quoting https://www.irs.gov/Individuals/International-Taxpayers/Totalization-Agreements https://www.irs.gov/Individuals/International-Taxpayers/Tota... : > The United States has entered into agreements, called Totalization Agreements, with several nations for the purpose of avoiding double taxation of income with respect to social security taxes. These agreements must be taken into account when determining whether any alien is subject to the U.S. Social Security/Medicare tax, or whether any U.S. citizen or resident alien is subject to the social security taxes of a foreign country. You'll notice that's a much smaller list of counties. (When I went to the local Swedish tax office to request a copy of the declaration that I needed to include in my US tax forms, to say I was covered under the Totalization Agreement, they didn't know at first what I was talking about. Asking for the form also must have triggered something, because a month or so later I got a phone call from the Swedish tax office asking for why I needed that information, and asking for a copy of my most recent US tax forms.)