To say that most of the world's population has some Abrahamic blood is plausible but to say that a specific group (like the English -- they're not too bad, really) are the only ones descended from the Israelites seems elitist and incorrect and not in Christ's teachings of the brotherhood of man. Spiritually, of course, Christians of all hues are God's people as you correctly state.
Maybe the Brits have the preponderance of Israelite heritage. I just wouldn't know, see? There have been myths floating around for centuries. Maybe those myths have some basis in fact. Maybe they don't. Nobody knows.
I'm a Christian and I believe in both testaments of the Bible. I believe when God makes a promise, He keeps it, and thus I'm not able to ignore Hosea, nor the prophecy of the sticks, which says the same thing.
But, there is one thing that intrigues me and the reason I decided to explore the issue. IF it is true that the tribes ended up populating Europe and became the dominant heritage there, what are the consequences on the world stage today?
To me, it gives solid foundation for the assistance to and the protection of the Jews in Israel, with a presumption of a reconciliation of both. That would fulfill the prophecies.
I like that notion. Many don't. To each his own. I still don't see what's so objectionable about that.