The Lord made it clear, the land this gospel of the Book of Mormon came forth on was Book of Mormon land which was prayed over by Book of Momon prophets:
47 And I said unto them, that it should be granted unto them according to their faith in their prayers;
48 Yea, and this was their faith—that my gospel, which I gave unto them that they might preach in their days, might come unto their brethren the Lamanites, and also all that had become Lamanites because of their dissensions.
49 Now, this is not all—their faith in their prayers was that this gospel should be made known also, if it were possible that other nations should possess this land; 50 And thus they did leave a blessing upon this land in their prayers, that whosoever should believe in this gospel in this land might have eternal life; (D&C 10, date Summer 1828)
The following identifies Gentile churches:
54 Now I do not say this to destroy my church, but I say this to build up my church; 55 Therefore, whosoever belongeth to my church need not fear, for such shall inherit the kingdom of heaven.
56 But it is they who do not fear me, neither keep my commandments but build up churches unto themselves to get gain, yea, and all those that do wickedly and build up the kingdom of the devil—yea, verily, verily, I say unto you, that it is they that I will disturb, and cause to tremble and shake to the center. (D&C 10)
Which was shown to Nephi also:
17 For thus saith the Lord God: They shall write the things which shall be done among them, and they shall be written and sealed up in a book, and those who have dwindled in unbelief shall not have them, for they seek to destroy the things of God.
18 Wherefore, as those who have been destroyed have been destroyed speedily; and the multitude of their terrible ones shall be as chaff that passeth away—yea, thus saith the Lord God: It shall be at an instant, suddenly—
19 And it shall come to pass, that those who have dwindled in unbelief shall be smitten by the hand of the Gentiles.
20 And the Gentiles are lifted up in the pride of their eyes, and have stumbled, because of the greatness of their stumbling block, that they have built up many churches; nevertheless, they put down the power and miracles of God, and preach up unto themselves their own wisdom and their own learning, that they may get gain and grind upon the face of the poor.
21 And there are many churches built up which cause envyings, and strifes, and malice. (2 Nephi 26)
Which found fulfillment in the Burdened-over District of Western New York at the time it came forth, and continues to be fulfilled in America.