Second, your characterization of murders in the US is not very accurate. There’s no shame in that, because most people only know what the news reports and the reporting is generally terrible. Even when there is no deliberate distortion of the facts the journalists just generally don’t know what they’re talking about.
The simple fact of the matter is that that in the USA, most murderers are black. Black Americans commit the majority of the violent crime. Hispanics are somewhere in the middle, and asians have a lower crime rate than whites. And guess what? It is entirely appropriate to say that black Americans have a different culture than white Americans. Everyone already knows that.
It is also appropriate to point out, although it may be less well known, that there are multiple cultures within the black Americans. One of those cultures is the mainstream “ghetto” culture whose characteristics you know. Another is characterized by higher educational attainment, greater family cohesion, greater wealth, and greater access to intergenerational wealth, different accents, manner of dress, different cultural interests (music and whatnot), and a vastly lower rate of violent crime. This is the culture that has successfully integrated into American society.
As far as I know we don't have good statistics about the relative crime rate of immigrants to the US compared to native–born Americans. Our stats tend to focus on race rather than country of origin.