Some US citizens work in the UK. While there, they are under the authority of the UK. Whether the authority in the UK is elected or not really doesn't matter. Now, being US citizens, they need to pay a portion of their earnings to the US Social Security so they can collect the benefits when they retire.So, why are matters related to the Social Security System of the USA an issue for the UNELECTED monarchy of the UK ?
Still no answer !
Now, the UK has a system which is also called Social Security. Two systems.
Both called "Social Security". One in the US, and one in the UK.
Ordinarily, a portion of earnings in the UK is set aside for the UK Social Security.
A US citizen working in the UK would have to pay twice: once under the US Social Security rules, once under the UK Social Security rules. That's not fair.
Both governments have decided that this was not fair, and have agreed to keep their laws coordinated so that US citizens working in the UK and UK citizens working in the US don't have to pay twice.
The US makes the rules for US Social Security, and the UK makes the rules for UK Social Security. So the UK may have a Social Security Act, and the US can have a Social Security Act, and they can be completely separate things.
Because of the agreement, one government may voluntarily change its own rules to more closely align with the rules of the other government.
But the UK government has an interest in the US Social Security because they host US citizens working there, and have UK citizens working in the US. They don't want their citizens to have to pay into a system they won't be using.
But there are two systems. The UK government makes the rules for the UK Social Security, and the US makes the rules for the US Social Security.
The fact that they have the same name does not make them the same system, any more than two guys named John are the same person.