When Lehi, who lead his family away from a decadent Jerusalem across the ocean to the Americas, left his final blessings on his children, he made a prophecy about this new land that his children would inherit:
Wherefore, this land is consecrated unto him whom he shall bring. And if it so be that they shall serve him according to the commandments which he hath given, it shall be a land of liberty unto them; wherefore, they shall never be brought down into captivity; if so, it shall be because of iniquity; for if iniquity shall abound cursed shall be the land for their sakes, but unto the righteous it shall be blessed forever.
This certainly happened in relation to the descendents of Lehi, who lived in liberty in the western hemisphere for nearly a thousand years, but were destroyed or enslaved in short order as they turned iniquitous.
It can also be seen that as long as most of the people who came to America were devoted to God and keeping his commandments, this was a land of liberty. The American Revolution is a good study of how a nation shouldn't have survived in the face of so many obstacles, overcome through divine intervention. It was a point of some strange pride that "God Bless America" could be relied upon to save and prosper the Union. People traditionally went to church and prayed in gratitude for the gift of liberty and prosperity, which they received.
Now, we are beating a fast retreat from God as a people. More Americans identify as atheists; They seek to prop up government as their protector and guarantor of peace and liberty, which is increasingly elusive and even undesirable to a growing number of urbanites. Many believe that God isn't interested in us, even if God exists at all, so they flout his commandments openly and with a pride in their ability to do so.
Lehi makes it clear that "if iniquity shall abound" (and it surely does), "cursed shall be the land..." The American nation has been so trusting that good things will always come, as they always have. However, the blessings we have always enjoyed will turn into a cursing, to which we have little experience. I expect the kind of horrors that we have never known in our country.
To counter this cursing, we need to be righteous and encourge our neighbors to do the same. We all need to study our Bibles again, re-learn what God wants us to do, re-enshrine his commandments to us, and them reclaim the blessings for ourselves that our larger society has rejected. "...but unto the righteous it (this land) shall be blessed forever."