I suspect that there is a slight conspiracy: "the first rule of science fiction writers club is that you don't talk about Stapledon". It inspired most of modern science fiction but very few outside of the field have heard about it. Accelerando, The Shape of Things to Come, 1984, That Hideous Strength, 2001, Blindsight, most of HP Lovecraft, etc... all borrow from him.
To C.S. Lewis and AC Clarke's credit, they do acknowledge the importance of Stapledon to their work.
Do you think 'Last and First Men' changed your perspective?
The timescale of the book is staggering. It's like that 'pale blue dot' picture.
http://www.wscribe.com/parables/pass.html
For those that haven't read the book or that don't have access to it, the book follows the 'first men' (us) and their successors across billions of years. Not all movement in time is progress and not all change is natural. Very much recommended, I won't write any more here to not spoil the book for future readers.
Cut them some slack. If they say anything different it's likely some lunatic will label them "unamerican". While the country, as it presently stands, will not endure for long in a planetary timescale, we'll be fortunate if some of the core ideals behind its foundation last for a longer time and help guide our descendants into the deep future.
That isn't entirely true, Lem praised the work of Philip K. Dick (American)[0][1] and Olaf Stapledon (English). He has two essays in which he analyzes Stapledon two great works: Last and First Men, and Star Maker[2].
I think you might also be suffering from a filter. The best of Polish writers were translated, whereas you have access to the glut of all American writers. It is probably true that there was a greater number of bad American writers.
[0]: http://www.depauw.edu/sfs/backissues/5/lem5art.htm
[1]: Dick returned the favor by reporting Lem to the FBI as a communist conspiracy against the west. Arguing that Lem was in fact a committee and not a person. Read the letter here: http://english.lem.pl/faq#P.K.Dick
[2]: http://dpuadweb.depauw.edu/icronay_web/lem%20stapledon.html