I agree that the left in the US you refer to hasn't done enough, but as you said, they're fighting a major battle against corporate power and that's had very significant effects on the organizing power of of Americans in general, in a number of ways that I'm sure you're familiar with. Huge attacks on unions, teachers, schools, students, workers in the public sectors and so on, which has crippled the power of the "left".
I was just reading earlier today about the mass government protests in Argentina and Hong Kong, and those movements are largely empowered by the groups I just mentioned. Without a focused, organized effort from these sectors in the US, it will be very hard to achieve significant change.
As far as the organizational might of the Tea Party and similar groups, a large part of the reason their organization is so effective these days is that parts of the business class is now making major efforts to mobilize them and it's been extremely successful.