Peace upon you also bro Pops
The children of Israel were a tribe from the loins of Jacob and those who followed him as a prophet pf God (pbuh). The rest of the known world was populated, from Africa to China.
Are the Africans and the Chinese also the lost sheep? How about the Aborigine? Or the Sami? Or the Lapp? Or... I can go on. Point i'm making is that, according to biblical teachings, I found the following really interesting:
Table of Nations:
Noah pbuh had three sons who were tasked with the repopulation of earth.
Ham, Shem and Japeth were their names, may God be pleased with them.
Ham settled the horn of Africa, Shem, the fertile crescent of the Middle East, and Japeth, The North Lands beyond the Caucuses, according to Judeo-Christian exegetes.
From Shem, come the line of Prophets and Messengers as you are taught in your scriptures, and so, there are still two thirds of the human populus which remain outside of the fold of revelation.
Let us now just focus on the Shemitic lineage, from whom we find the lineage of Prophets and Messengers.
From the Shemites, come many nations, and tribes, all identifying under one genetic marker of origin, tracing back to Shem. Nations such as the Akkadians, Assyrians, Babylonians, Phoenicians, Mesopotamians etc - from whom we derive the modern set of semitic races such as the Hebrews and the Arabs.
The above mentioned, are the limits of Semitic influence. And from these, the first set of revelations after the flood were given to Abraham pbuh, and from him descend the lineage of Prophethood through his seeds which God clarified for us in the Old Testament.
The argument that the lost tribes of Israel is the whole world - doesn't stand because one has to also factor in the other two sons of Noah pbuh, and their offspring, of which the Old Testament teaches that Japeth's lineage would be the most numerous of all... yet, from the line of Japeth, we get Magog - the enemy of God.
So no, the whole world cannot be Israel. Israel, in context are semitic in origin an followers of scripture - according to the OT.
And if one is not of that bloodline, one cannot be semite.
Hope this helps,
God bless,
Scimi
EDIT:
I think one distinction we must make here is the following:
One does not have to be a semite to believe in One God and the Prophets and Messengers (peace be upon them), hence one does not have to be a semite to come to belief.
The importance of the Semitic heritage is that the lineage of Prophets and Messengers descend from this line. I think this goes over the heads of most. The guradians of the Scriptures have always been Semites post flood.
Scimi