1) The key to the distribution of Japheth, Ham and Shem is that Shem is based in the Middle East, Ham is primarily to the south and Japheth is primarily the peoples of the north (the isles of the Gentiles).  The world kingdoms are associated with different families: Egypt (Ham through Mizraim), Assyria (Shem through Asshur), Babylon (Shem through Arphaxed), Medes and Persians (Japheth through Madai and Shem through Elam), Greeks (Japheth [Jupiter] through Javan), and Romans (Japheth through Javan).  Japheth must come to Shem for blessing (Gen. 9:27; Zec 8:32).
 
2) Japheth is not Japan.  Note the only similarity in consonants are the 'j' and the 'p,' plus this is not the real name of the country.  Japheth is the father of many nations through seven sons, not a single nation.  The Saxons perpetuated their ancestor as Iafeth (http://www.soundchristian.com/man).  Rather than Britain/USA being populated by Semites as you say, they are populated primarily by descendants of Japheth. http://www.imninalu.net/2history03.htm  The temples of Washington DC and the state capitols give evidence of a Greek/Roman system.
 
3) Celts are from Japheth through Gomer.  Note the parallel C(G)-M-R of Cymry (or Cymru, pronounced 'Coomry,' what Welsh call their country) http://www.regia.org/history/welsh1.htm, and Cimmerian, Gimirrai and Gomer. http://www.imninalu.net/2history03.htm
 
4) Saxons are from Japheth through Magog through the Schythians (Saka) http://www.imninalu.net/myths-brits.htm.  "The Saki called themselves the Sakasenoi, which we know as the Sachsens or Saxons." (http://www.soundchristian.com/man).
 
5) Saxons are not "(I)saac's sons." Israelites are Jacob's sons.  Yits-chaq has no similarity to "sax."
 
6) Danu is an Indian/Irish river goddess. http://en.wikipedia.org/wiki/Danu_(Irish_goddess).  Names of rivers in Europe that have Dan in the name are not derived from the tribe Dan (neither is the Jordan river).
 
7) Britain has nothing to do with the Hebrew b'rith.  A more likely source of the name Briton is Brutus (a descendant of Elisha, son of Javan, son of Japheth) the first king of Britain's mainland, arriving about 1100 bc (http://www.soundchristian.com/man).
 
8) Queen Elizabeth may have been coronated as Queen over "Israel," but Satan is a liar.  Japheth is not the son of Noah with the blessing.  I understand that Satan would like to take the blessing from the rightful owner of that blessing.  The kings of the earth take their stand, the rulers counsel together against YHWH and against his anointed (Psalm 2:2).  I see significance in Zechariah 8:23.
 
Zec 8:23 Thus saith YHWH of hosts; In those days [it shall come to pass], that ten men shall take hold out of all languages of the nations, even shall take hold of the skirt of him that is a Jew, saying, We will go with you: for we have heard [that] God [is] with you.

 

9) When the Northern tribes split, Jeroboam to make sure that his people did not worship in Jerusalem, instituted a religion of Egypt (1 Kings 12:28, 32).  This led to YHWH's punishment, but not before many true worshippers of YHWH moved to Judah.  History shows this movement was particularly rapid at the time of the Assyrian captivity when Jerusalem and surrounding regions increased in population 3-4 fold. http://www.theology.edu/journal/volume4/BritishIsraelism.htm

1Ki 12:28 Whereupon the king took counsel, and made two calves [of] gold, and said unto them, It is too much for you to go up to Jerusalem: behold thy gods, O Israel, which brought thee up out of the land of Egypt. 1Ki 12:32 And Jeroboam ordained a feast in the eighth month, on the fifteenth day of the month, like unto the feast that [is] in Judah, and he offered upon the altar. So did he in Bethel, sacrificing unto the calves that he had made: and he placed in Bethel the priests of the high places which he had made.

11) Cyrus' call to rebuild Jerusalem went out to all Israel who were willing.

2Ch 36:22 Now in the first year of Cyrus king of Persia, that the word of YHWH [spoken] by the mouth of Jeremiah might be accomplished, YHWH stirred up the spirit of Cyrus king of Persia, that he made a proclamation throughout all his kingdom, and [put it] also in writing, saying,
2Ch 36:23 Thus saith Cyrus king of Persia, All the kingdoms of the earth hath YHWH God of heaven given me; and he hath charged me to build him an house in Jerusalem, which [is] in Judah. Who [is there] among you of all his people? YHWH his God [be] with him, and let him go up.
 
Ezr 6:17 And offered at the dedication of this house of God an hundred bullocks, two hundred rams, four hundred lambs; and for a sin offering for all Israel, twelve he goats, according to the number of the tribes of Israel.
 
10) The terms Jew and Israel are used interchangeably in the Scripture. Below is an example from Acts where the Jews (men of Israel) knew who they were and came to Jerusalem to worship.

Act 2:5 And there were dwelling at Jerusalem Jews, devout men, out of every nation under heaven. Act 2:22 Ye men of Israel, hear these words; Jesus of Nazareth, a man approved of God among you by miracles and wonders and signs, which God did by him in the midst of you, as ye yourselves also know:

12) James did not consider the Twelve Tribes "lost," but rather scattered abroad (James 1:1).  Both Houses were scattered.  The Jews (made up of all Twelve tribes) are scattered.  Israel may include the Gypsies.  Various other tribal groups in Africa and Asia have been identified with Israel and allowed to immigate under the Law of Return.  Genetic studies concerning a physical Israel are summarized in the following link. http://www.khazaria.com/genetics/abstracts.html  However, I see salvation not based on race, but on obedience to the Everlasting Gospel.