"When you’re UK resident you’re normally taxed on the arising basis of taxation. This means that all your worldwide income and gains will be taxable in the UK. Therefore, even if your foreign income and gains have already been taxed in another country they will still be taxable in the UK and you must declare all of your foreign income and gains on your tax return."
https://www.gov.uk/government/publications/residence-domicil...
The difference is that a UK citizen can become 'non-resident' by moving permanently abroad and there is a 'non-domiciled' option that is wildly complex legally but allows taxation on a remittance basis.
The US tax code applies to its citizens wherever they choose to live in the world with IIRC no exceptions short of renouncing citizenship.