I have some critique of Strong over a few lines which, I think, indicate some level of West-centrism or Orientalism. For example:

Their situation is the more distressing because for most of our Western world the past hundred years has been what John Strachey aptly calls the 'century of the great hope.' [...] Especially America— where [there was] a continent-wide expansion into lands of vast wealth [...] Did not the great lands of America [...] offer the basis for a good standard of life for everyone—an 'American standard'?

This part, at face value, is factual — this is how the US proletariat understood their existence in the country. But I think, during Jim Crow when this book was written, it is unfortunate that Strong does not connect this apparent prosperity (for whites) to chattel slavery and indigenous genocide.

Furthermore, this line rang Orientalist to me:

Even today, do not hundreds of millions of people—those great suppressed races of the East—find life's processes so fundamentally evil that their essential faith is Buddhism in which Nothingness is bliss?