A bit of advice I have given elsewhere on this forum is when the time comes to make Roth distributions that the IRS rule is that for overseas customers there is a mandatory 30% withholding even though no taxes are due. Vanguard told me that this applies to all IRAs regardless of an individual’s tax situation. (There are situations where a Roth distribution is taxable)
However, Vanguard does allow a street address where you reside and a different correspondence address. For my correspondence address I now use the same US forwarding address my daughter uses. (I did use her US address until she moved to England). I got caught out having to make a 30% withholding the first time I made a Roth distribution but with a US correspondence address that is not an issue, I can choose any withholding I want, including 0%.