Do you teach? Or are you a student? And what are you teaching and/or studying?
I'm asking because if you're in academia, it's quite odd that you asserted that "US law cannot compel someone in Britain to be treated as a citizen of the US" when such can quite clearly be proven false, as I've easily done.
No, you have not easily done it, nor done it at all. US law does not control the UK, nor the UK law control the US. When there is a disagreement, it falls under international law. International law uses the laws of the disputed countries as a starting point to use in resolving the conflict.
UK law can nor require someone born in the US with a UK subject parent (Obama) to serve in their military, nor can it prevent him from running for office. US law controls that. It just doesn’t work that way. If Mexico declared all US citizens to also be Mexicans, it could not compel us to all serve in its military or pay taxes to Mexico.
I’m taking paralegal classes. There are no classes in US citizenship, although I took a class in immigration law recently. However, its focus was on what is required to get a green card or to become a citizen. Those who were born citizens were not part of the subject matter.