I think there’s a difference between low social mobility and class stratification, if only in that the second happens when the first becomes more established and fossilized. A class system would usually oppose entry into a higher class by the nouveau riche, whereas successful entrepreneurs seem to have a high status in the US. They will obviously be in the extreme minority though, as the advantages of being wealthy and well connected seem to be greater than before (although they will always be important in almost any culture). On the other hand, the means of reaching that level (e.g. through education) seem to be getting more and more strained, while crippling debt or the fear of debt will stop many of those who would otherwise succeed from reaching their potential. Meanwhile, it is becoming easier for the wealthy to gain more wealth, or to use it to gain political power. I suppose an enduring idea that America is a meritocracy leads to the idea that things are as they should be and the poor deserve what they get. I’m not sure if I would consider the US to be fully stratified at this point, although it probably depends a lot on where you live. The last few decades have certainly highlighted the importance of high quality public education available to everyone as a way of fighting class stratification.
