If you have a relative living in the UK die and leave an inheritance (eg over $1m), how much total US tax would you pay? How much more would you pay vs being in the UK?
There is no US tax of any kind on inheritances, whether received from the estate of a US tax resident or someone resident outside the US. There may be death duties etc to be paid in the UK but in the US, these are paid by the estate before the beneficiaries get their bequests from the estate. If this is different in the UK, then there may be taxes to be paid in the UK.