Have you read this interesting piece by Michael Lind?:

From the beginning, attempts to create a universal welfare state in the U.S. have been thwarted by the fears of voters that they will be taxed to subsidize other Americans who are unlike them in race or ethnicity or culture.
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Since the 1964 Civil Rights Act destroyed formal white supremacy in the U.S., every attempt to expand traditional social insurance in America has failed.
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Could it be pure coincidence that the most generous welfare states in the world have been those of ethnically homogeneous Nordic countries where, until recent immigration, nearly everyone was related to everyone else?
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If the politics of ethnic diversity makes movement in a universalist, social democratic direction impossible in the U.S., then the alternative might be to mandate that all employers provide certain benefits to all employees, with no exceptions.

Beyond the possibility of undue fatalism in this account of the inevitability of systemic racism in a racially diverse society, I think Lind fails to account for another distinctive aspect of our society : the U.S. epidemic of the religionism/superstition:

the United States ranks next to last in acceptance of evolution theory among nations polled. …the number of Americans who are uncertain about the theory’s validity has increased over the past 20 years.

The pernicious popularity of metaphysical ideologies in this country makes it difficult to sustain the kind of epistemological common ground which enables reasonable debate. How can you have a productive dialogue with someone more interested in blind belief (“we’re #1!”) than material facts?

Well as you say, it’s not a diversion, it is a critical component. Racism has been exploited by conservatives in particular as a way to defeat programs for the lower economic classes. You don’t get a lot of support from lower middle class whites for trashing programs that will help them, but if those people benefit, you have a wedge to turn them against their own interests. Currently the “illegals” stand in for the African Americans because it’s not considered good form to be overtly racist, but it doesn’t take much to read between the lines.