Wherefore, it was wisdom in the Lord that we should carry them with us, as we journeyed in the wilderness towards the land of promise. 1 Nephi 5:22 

The LORD had said to Abram, “Leave your country, your people and your father’s household and go to the land I will show you.
 “I will make you into a great nation
and I will bless you;
I will make your name great,
and you will be a blessing.
I will bless those who bless you,
and whoever curses you I will curse;
and all peoples on earth
will be blessed through you.”
So Abram left, as the LORD had told him; and Lot went with him. Abram was seventy-five years old when he set out from Haran.  He took his wife Sarai, his nephew Lot, all the possessions they had accumulated and the people they had acquired in Haran, and they set out for the land of Canaan, and they arrived there.
Abram traveled through the land as far as the site of the great tree of Moreh at Shechem. At that time the Canaanites were in the land.  The LORD appeared to Abram and said, “To your offspring I will give this land.” So he built an altar there to the LORD, who had appeared to him.  Genesis 12:1-7

According to the Book of Mormon, God promised a land to Nephi that he should take his family to around 600 BC.  A "land of promise" as it is called.  That land turned out to be The Americas, which Nephi and his family, according to Mormon history, sailed to.

But what happened to the other Promised Land, promised to Abraham in Genesis?  Israel.  Did God change his mind?  Did God break his promise?  All that work to get the people to Israel just thrown out the window.  The reason given for the change in "lands" had to do with the Jews disobedience. 

God's people have always been disobedient!  God worked with them anyway, showing them grace, getting them through the desert for 40 years, then fought with them side-by-side to get them into the country.

If God had to start a new promised land, that means either:

• God was mistaken about the first promised land and thus had to break his promise for that land
• God changed his mind because he was mad (scary to think God is so emotional and easily offended)
• God lacked in grace and could not forgive people for their disobedience

That brings up another question, then why did Jesus, 600 years later, come to Israel if he's given up on the old Promised Land?  Why didn't Jesus come to the Americas first and ignore Israel?