Wow, knives are really out for Rishi.
Can't you just hate Sunak for being a Tory who endorses Tory policies, why must PP distort & make shit up?
Sunak isn't tax domiciled in USA -- USA doesn't have the concept of being domiciled for tax obligation purposes. USA does have foreign-earned income exclusions IF you prove you have foreign residence 90% of the year. That is as good as it gets, and only if you testify to living outside USA.
A USA green card 'allows' residence, it's not the same as being resident. I'm sure he uses the foreign-residence allowance just like I do on his income earned in UK/abroad. That's a legal declaration that he lives outside USA.
With GC-holder-status comes the liability of declaring his income worldwide and paying tax on it if above certain thresholds. It's the same filing requirement if Sunak merely has a bank account in USA, btw. Given the inherent security of MP's jobs & the difficulties of securing green cards, I can perfectly understand him keeping that option open.
iirc, Johnson renounced because of capital gains payments to be avoided in future when he next sold his primary residence. There is minimal US federal exemption on capital gains taxes from sale of primary residence. It was nothing to do with FATCA. FATCA is not that hard a form to file, tbh, it's paperwork rather than extra tax anyway. Isn't Johnson cash-strapped ? He might not have been liable to file FATCA, if he only has debts, shares in businesses but little cash.