There is a lesson for us in the fact that Christ appeared to the Nephites a year after his resurrection. Did he promise to appear to them? Yes.
But the scripture was still fulfilled:
Ether 12:7 For it was by faith that Christ showed himself unto our fathers, after he had risen from the dead; and he showed not himself unto them until after they had faith in him; wherefore, it must needs be that some had faith in him, for he showed himself not unto the world.
So, yes, Christ appeared to them, but not until they had sufficient faith for him to do so.
And so it is today.
Joseph Smith said “Could we all come together with one heart and one mind in perfect faith the veil might as well be rent today as next week, or any other time”.
Would there have been unspeakable trials among the Nephites if they had been ready to receive Christ at the day of his resurrection? No, he would have held them in the palm of his hand.
But as it was in their day, so it is in ours. The Lord has declared of us:
D&C 84:57 And they shall remain under this condemnation until they repent and remember the new covenant, even the Book of Mormon and the former commandments which I have given them, not only to say, but to do according to that which I have written—
58 That they may bring forth fruit meet for their Father’s kingdom; otherwise there remaineth a scourge and judgment to be poured out upon the children of Zion.
And so we, like the Nephites, may have to endure things as horrific as what they experienced until we will repent as the Nephites did, and there is a people for the Lord to come to that will not be wasted at his coming.