If we were to divide up the country into the subsidizers and the subsidized (whatever that means), why must we pick ethnicity as the dividing feature?
Or, to put the question differently, if America were ethnically homogeneous, would it follow that there wouldn't be a taker/maker split to "damage social cohesion"?
To give an example of a different dividing criterion, how about the disparity between federal tax revenue and federal spending per state? Taxpayers in "red" states get a 4.0 percentage point better return on investment in federal taxes than "blue" states [0]. If one were to accept your claim that "identifiable groups with different socioeconomic contributions" (a condition states surely satisfy!) make welfare impossible, one would have to conclude that the American welfare state is broken because it has states!
[0] https://wallethub.com/edu/state-taxpayer-roi-report/3283/