Why are blacks marginalized in the United States of America?

Have you ever considered the logic, if any, behind opening the floodgates to unskilled, illiterate Central and Southwest Asians (a/k/a Eastern & Southern Europeans) in the late 19th and early 20th centuries?  
 

I mean, there were enough Blacks in the South, Native Americans everywhere, and East Asians in the West to do any needed work, who were already citizens, and knew the language, right?
 
The issue was "quality", not quantity.  Black men and women, teeming masses of skilled, energetic people who had just fought and won their freedom in the biggest slave revolt you’ve never heard of, a/k/a the Civil War, were poised to take over. 
 
Abraham Lincoln, yo’ White Savior, after "freeing" you (from states that weren’t under his jurisdiction), had proposed to ship you to Central America. 
 
That didn’t happen, so they had to dilute the population by replacing the millions of white men who died in the war with immigrants, for whom the first English word they would ever know would be the "N-word". Now you know why. They were teaching them that the Black man, woman and child were who they were there to beat out.
 
Long story short, the answer is, "Because White Supremacy."
 
And the US isn't the only country...