While in theory anyone in the US can make it with sufficient effort, the reality is that some people get economically shat on through no fault of their own. Our national mythology/culture doesn't take this into account, and as a result we're incredibly vicious towards those who struggle.
As more and more capital needs less and less labor to be profitable and create value, we're going to need to find more effective ways to make sure everyone's needed, or things have a potential to get much worse before they get better.
EDIT: As others have noted, we also severely undervalue social capital, so we by and large firesale it to accumulate more material value. We work more instead of spending time with friends and family, thereby dangerously isolating ourselves. Thank you all for pointing this out.