The state of theological debate in today’s America - is God male or female; is Jesus white or black.
Who cares, as long as he comes soon.
The lineage of Jesus is not a trivial fact. His lineage is from the Royal line of David and that lineage has prophetic importance. When He returns, He will be a king because he inherits David’s throne over all Israel, that is over all the tribes.
Luke 1:32:
He shall be great and shall be called the Son of the Highest. And the Lord God shall give Him the throne of His father David.
Mark 11:10:
Blessed is the kingdom of our father David, who comes in the name of the Lord! Hosanna in the highest!
It is an excellent question to ask where are the 13 tribes of Israel today. We know where one is, that is Judah. But where are the rest. They are somewhere on earth at this very moment, and indeed it is prophesied that they will be under attack at the end of the age.
See for example:
The Lost Tribes of Israel
Why They Matter
http://www.ucg.org/beyond-today/beyond-today-television-program/the-lost-tribes-of-israel-why-they-matter
or
Finding the “Lost” Tribes of Israel
http://www.tomorrowsworld.org/magazines/2008/november-december/finding-the-lost-tribes-of-israel