It's largely because English-speakers developed the fundamental foundations of civilization like rule of law, representative government, and religious and economic freedom. And those ideas flowed into the magnificent US Constitution that set in motion the truly exceptional economic and political history of this country.
You could say that it's the Anglophones who invented freedom. In addition to the political ideas from England, our Constitution, and the influx of Northern Europeans with a strong work ethic and intelligence made this country great. The primacy of self-reliance, family, community and church/temple used to be the backbone of society -- not dumb-ass bureaucrats in far off Washington.
Sadly, Africans and African Americans are against this intellectual heritage and these fundamental ideas. They don't embrace Anglo values that bring freedom and prosperity. They don't see it. They don't get it. They fight against it. They might as well be from planet Pluto politically, they are so out of touch!
It's because there is no racial history of liberty, guaranteed rights and freedoms in the history of Africans or African Americans (and Latinos too to a large extent). They mostly know tyranny and poverty (and slavery). Theirs is a history of poorly-educated peoples, failed governments, failed states, tyrannical and irrational leaders, poor economies, poverty, and suffering. That continues to this very day. Even when there is nominal democracy, voters fall for the false siren songs of populist politicians that ultimately bring ruin to their countries. It's the most obvious thing in the world. Just survey the continent of Africa (and Latin America). Just look at African American communities and the cities where African Americans are a majority. Not much has changed.
Blacks have embraced, and will continue to embrace, Democratic politicians who make nice-sounding promises but who only line their own pockets and ultimately hurt their own people and country. They'll even re-elect known criminals. Detroit is a 60 year history of this behavior. Ruin is the result. Many of these people might be nice and well meaning but they vote for ruinous politicians and continue to do so despite continued failures. Black politicians are mostly ignorant, corrupt and dishonest and have bought you the likes of Detroit and the crime-ridden cities like Washington DC and Memphis. All are Democrats!
All African American Leaders are Socialists and Communists and Against America
Remember nearly all US black leaders support the likes of far-Left Hugo Chavez and communist Fidel Castro as if those people were some kind of saviors. Hollywood and black "leaders" continue to admire Chavez despite the fact that Venezuela is in ruins. And Castro was welcomed in Harlem in the early 90s with thunderous applause of all the black "leaders." Even Martin Luther King was a Socialist. They are all against the philosophy of the founding fathers. Leftists everywhere bring ruin to their countries. And basically there are no political success stories at all in Africa. And black people in America have shown nearly no ability to learn.
Just look at how Obama is completely incapable of learning or adjusting. He is supposedly educated but shows no sign of it. He is really an enemy of America. Name one thing that he hasn't made worse -- whether it's domestic policy or our international standing. Obama is an enemy of America.
African Americans will continue to burden and hurt the the USA for as far as the eye can see. There is no sign that they will ever "get it." They can't embrace political freedom because too many of them are completely and utterly incompetent, ignorant and they can't handle freedom.