Of course your points are worthy of discussion, as this is a very complex situation with various factors.
But in response to your first point regarding the Irish, Italian, Greeks. One obvious and fundamental difference that cannot be ignored. They were, for the most part, white.
In terms of getting a chance, a second generation Irishman had a much greater chance than a guy whose parents or grandparents, if we go back to the start of the 20th century, were slaves.
And this institutionalised discrimination lasted in every facet of American society for a long time. It even does to a certain extent today.
America has not fully reconciled over their past regarding slavery. And that couldn't be more evident than what we've been seeing lately.
What about Jews and Asians ?
Granted Jews in America are for the most part Ashkenazi but in all fairness historically they've had a pretty rough ride in any country the diaspora is found. In America they positively thrived , despite anti semitism being a feature of 'American Racism' too.
American Asians are a far more interesting point of reference though. The Chinese are a massive yet almost anonymous part of American history . Again they endured appalling racism and discrimination . Didn't seem to hold them back though.
But you are correct though about slavery and I mentioned earlier that is not a footnote or something that can brushed off as something that happened years ago. There was a book called 'Slavery by another name' by (ironically) a lad called Douglas Blackmon and there in he describes how although slavery was abolished in the 19th century is endured by other means for quiet some time afterwards right into the 20th century. It cannot be argued it has left a serious scar on generation after generation of African Americans.