Blake was not of their camp. He was more a mystic and a romantic (which can be criticized, too, but they're not socialism). His "'til we have built Jerusalem" was no more built on a Socialist blueprint than America's "alabaster cities [which] gleam,undimmed by human tears."
He was repelled by the godless materialism of his time. This was real, jackbooted oppression of the poor, deprived of land and a living, family, God and all. This was no propagandist's fantasy.
The economic crimes which accompanied this phase of British capital accumulation and "development" --- that crimes that "put them on the map," if you will --- were crimes that were identified in the Bible --- as Blake was aware---as calling out to God for vengeance:
Exodus 22:21
[The Lord says]Ye shall not hurt the widow and the fatherless: If you do hurt them, they will cry unto me, and I will hear them cry, and my fury shall take indignation, and I will strike thee down with the sword.
I’m not accusing Blake of radical egalitarianism but of “Romantic” pipe-dreamery.
America’s alabaster cities weren’t built solely on the oppressive labor practices of English industrialization. Feudalism had reigned in England for centuries, and merely shed its ermine for tweed when industry supplanted agriculture. America had rejected the feudal structures of the Mother Country and even though it indulged some of the same abuses, it did not go to the extremes Britain did in shunning its oppressive past.
We never empowered a Cromwell because we never needed one.