There is nothing in the Book Of Mormon that contradicts the Bible. The Book Of Mormon emphasizes the laws and the gospel. Very early in the Book Of Mormon "one wife and no concubines" is emphasized. The Book Of Mormon is "another testament of Jesus Christ" like it claims.
America's current greatness was prophecied in the Book Of Mormon thousands of years ago. It has several prophecies and thus meets the definition of scripture.
On the other hand, there is ample warning that a blessed people, a blessed land, a blessed country can lose it all by walking away from God and losing their way. That is a warning call to America.
In the Book Of Mormon Mother Mary is described as "fair and white." Jesus being depicted as white is thus not inaccurate. On the other hand Lord Rama and Lord Krishna both had dark skins. The very word Krishna means "Blackie."
The Book Of Mormon is supposed to act as a bridge to other scriptures beyond the Bible. First you open up to the fact that the Bible is not the only scripture. The Book Of Mormon, "another testament of Jesus Christ" is also it. Then you open up also to other scriptures like the Koran where God denies His own Son, and the Geeta where the Holy Father talks about Himself in the first person.
None of the scriptures contradict each other.
A biblical prophecy is that the Gospel will be preached in every nation on earth. That will come to be. But that is not to say the Bible will be the only scripture left standing.