The Brits are subjects.
Americans are [ostensibly] citizens.
The story happened in Britain, and the subjects were subjected to the government.
citizen noun
cit·i·zen | \ ˈsi-tə-zən
a legally recognized subject or national of a state or commonwealth, either native or naturalized.
"a Polish citizen" · "the rights of every citizen"
synonyms: subject · national · passport holder · native · taxpayer · voter