The Lost Tribe of Manasseh is the modern United States.
Jacob's prophecy about Manasseh:
1 Genesis 48:17-20
17And when Joseph saw that his father laid his right hand upon the head of Ephraim, it displeased him: and he held up his father's hand, to remove it from Ephraim's head unto Manasseh's head.
18And Joseph said unto his father, Not so, my father: for this is the firstborn; put thy right hand upon his head.
19And his father refused, and said, I know it, my son, I know it: he also shall become a people, and he also shall be great: but truly his younger brother shall be greater than he, and his seed shall become a multitude of nations.
20And he blessed them that day, saying, In thee shall Israel bless, saying, God make thee as Ephraim and as Manasseh: and he set Ephraim before Manasseh.
The blessing given to Ephriam and Manasseh upset their father Joseph because Jacob apeared to be changing the natural birthright promises.
The passage suggests that Manasseh would inherit Abraham's Great Nation promise while Ephraim would become a community of nations.