It isn't taught, because it is irrelevant at best and heretical at worse (e.g.the missing tribes are the British)
The word 'Jew' originally meant only the Southern tribes, but has expanded to mean all tribes.
The tribes are not lost, they are concealed among the Jews and God will reveal what each tribe each 'Jew' belongs to during the Tribulation and Millennial reign.
It isn't irrelevant to me at all nor do I think it is heretical. I do believe the tribes eventually settled in England then to America but that is my belief. You are welcome to yours.
The word 'Jew' originally meant only the Southern tribes, but has expanded to mean all tribes.
To many it has - they are wrong.
The tribes are not lost, they are concealed among the Jews and God will reveal what each tribe each 'Jew' belongs to during the Tribulation and Millennial reign
What you believe disagrees with what God tells us. It is your choice.