What I've ready written.
The white population of the U.S. would not create an egalitarian distribution of wealth with non whites. You could see fascism or herrenvolk redistribution of wealth among whites but a proper socialist movement would never gain critical mass among the vast bulk of very racist Americans. Especially of the 19th century.
Your definition of socialism you mean. Redistribution of wealth can occur without it being equal and it can occur by ways of only benefiting certain groups to the exclusion of others. If you view is that socialism can only occur wherein all racial and ethnic groups have distribution at equal levels, then you would be of the opinion that no group has performed a socialist economy or political system, something that no left-wing thinker that I know of, has claimed.
Regardless, the Longist movement in Louisiana offered many welfare programs for the African diaspora in the state that transcended even what was being offered in the New Deal at the time. Long's political machine was known to work actively with the NAACP, in regards to various aspects of African community needs, such as increasing numbers of African American nurses, construction of schools at better qualities, reading and writing classes for impoverished African American farmers and so forth. The Longist policies of free school supplies, free school buses, no property taxes below certain levels of income or property value, infrastructure projects and other topics were taken. Long even took direct action in attacks upon the KKK and other organizations more interested in tightening the state grip upon the minority community.
As we see though, the most popular southern politician perhaps in history, a certainly left wing one at that, was able to mitigate the race issue by way of focusing his discourse upon the general common folk and the farmers in the state and then pushing his attacks upon the major corporations and political establishment in New Orleans and the Hoover and FDR regimes. White farmers and poor folk in Louisiana were extremely enthusiastic for these policies, despite the lack of public discourse on race from Long and even what is seemingly a benign take on the issue. Long was certainly no Vardaman thus (a populist in Mississippi in the early XX century, quite known for his racialist agendas extending far beyond maintenance of segregation legally; though he was also a strong populist, anti-war and spoke of the interests of capitalism and so forth). Long gives mention as to why he was so successful or gives hints of it in his biography, wherein he says at around the age of 23 to a progressive compatriot of his who claims no progressive change can occur in the state of Louisiana due to the power of the big corporations:
'Personally, I feel that Louisiana and states like them, are the most progressive in the country, truly...' he goes on to explain that the people of the rural areas are more susceptible to support of radical policy change and even totally flipping the entire system and upending it. This at the time, his speech may have been influenced by the then recent Bolshevik rising Russia (which was a known topic among many of the farmers, Milo Reno of the Farmers Revolution spoke of it in his riots and Long mentioned that economic redistribution will come to the US, either as it had done in France or in Russia or peacefully by his politics) . Long mentioned even earlier in his book, that the key to economic redistribution was a society like the one he lived in rural Louisiana, wherein the people ideally shared and shared alike, where there was little conception of money or of need. He then describes the arrival of the major industries and their perverse effect upon the rural communalism that he seems to idealize. Connected to his later statement, he was saying that the true progressive agenda is not taken from intellectuals in the city, but from the lowest echelon of the economic ladder. He was perhaps the first major US politician to articulate this in a well understood fashion and as we see, he dominated local politics to a degree far surpassing almost any other known US politician and in what was a state with a strong racial consciousness, was able to implement a form of economic redistribution unto the minority populace that exceeded what occurred in the New Deal.
This is all to say that the issue is more complex than to say that the race issue precludes far-left movements from taking control. It most certainly had an effect in discouraging it, but it does not remove it from occurring. The main issue I see, the US held the basing for the far-left to take power, but did not possess the political machine to do so or people who were skilled enough to see it come to pass. Long is the only example wherein a politician resorted to the language necessary and also took to making himself dominant politically, creating a vanguard political cadre and then in his later years, conceiving of a military wing and a revolutionary containment to destroy slowly what he termed reactionaries and conservatives in his midst.