I have never bought into that whole theory that Black Muslims in America are like the Ansar of Madinah and the immigrant Muslims in America are like the Muhājirūn. The only thing similar about the 2 situations is the fact that  in both situations we are all Muslim,  the Muhājirūn migrated to a place (Madinah) and our immigrant brothers migrated to a place (America).
Other than that there's not much else in common. In fact, there are more differences than commonalities:
 The Muhājirūn migrated for the sake of Allah and to establish the living reality of Islam; whereas the great majority of our immigrant brothers who've migrated here have done so for economic reasons, islam being an afterthought,
 Black Muslims (so-called African-Americans) don't have any power or control. Therefore, we aren't in a position to be "the Ansār", helpers or supporters to those who've migrated here. In fact, we are the oppressed group who was kidnapped and brought here by force to build this country without compensation - then or now.
 The Muhājirūn - such as Mus'ab ibn Umayr - brought and taught Islam to the Ansār and for the most part are the reason for them accepting Islam. In other words, Allah used the Muhājirūn as a means of bringing most of the Ansār to Islam. Whereas Black Americans have always been embracing Islam in large numbers in spite of (not because of) the immigrant presence here.
 There was a legal, Islamically binding brotherhood established between the Muhājirūn and the Ansār put in place for the purpose of enabling the the immigrants, who've left most of their worldly possessions in Makkah, to reestablish themselves in Madinah. In America, the so-called African-American Muslim is the one in need of a brotherhood of this nature. The Muslim American immigrant doesn't have this problem. After taking advantage of the many free benefits (which they are very hush hush about) and are only available to them, they attend and finish university, get employment in lucrative professions and establish themselves in much less than a decade.
 There were tensions every now and then, but for the most part it was love between the Muhājirūn and the Ansār. It is even documented how the Ansār would give their immigrant brothers more than what was agreed upon and the immigrants would complain to the Prophet (may Allah bless him and grant him peace) because they felt that the Ansar were stealing all of the Divine rewards due to their hospitality and generosity. Our situation, for the most part, in this country is different than that.
Black Muslim communities around this country have been suffering from a subtle, quiet, unofficial, undeclared embargo, sanction or boycott. Many of our immigrant brothers in this country attended so-called African-American masaajid until enough of them "got their weight up" and were able to move out into the suburbs and open their own Islamic Centers. After, this many of them have never looked back. The so-called African-American Muslim, his leadership and his crumbling institutions are looked at with contempt or indifference.
Most of them would rather give their money to non-Muslims causes while they boycott us into extinction. We have imams, like Imam Jamil al-Amin, (who have historically fought for human rights, which in turn lead to the relaxation of the immigration laws which allowed most of the immigrants to come here in the 1st place) withering away in prison on trumped up charges, whose legal fund needs massive help; yet they can't rally around his cause. We have imams that are literally homeless! It would take 1 immigrant brother to write 1 check to rectify this situation yet I doubt it would happen. We have hundreds of Masjids that are in disrepair or need other types of logistical assistance and they have to watch countless fundraising campaigns sponsored by our immigrant brothers who raise millions of dollars. And these dollars float right past the Black Muslim communities (who really need it) and end up in the coffers of (mostly affluent) non-Muslims - many of whom don't even need it.
This could go on and on. In any case, I have never felt comfortable with that "Muhājirūn/Ansār" comparison. And we need to recognize the difference between an ideal and the reality on the ground.
May Allah unveil our "eyes" so that we see truth as truth, falsehood as falsehood. And may Allah rectify our collective situation!