Obama needs to do something. Anything. Standing up and saying that the U.S. is still a AAA Country isn't going to cut it. He needs to propose something. Heck, it could be a $2 trillion stimulus/jobs program. I know it wouldn't have a 1% chance of passing Congress but that isn't the point. History will judge harshly a leader who doesn't at least attempt to 'lead'. Obama just looks like a deer in the headlights.
He has proposed things the GOP has previously signaled openness to (a payroll tax holiday, infrastructure bank, new free trade agreements to spur job growth). You may not love those ideas and it doesn't matter since the GOP will fight whatever he proposes. He's also tried to calm any jitters from the downgrade by saying he'll be offering proposals to the Super-Committee and has threatened to veto any extension of Bush tax cuts that includes the wealthiest if there's no revenue in the SuperCongress deal (which circumvents a specific problem S&P had, even if it doesn't change the larger problem of partisan gridlock and the GOP taking the debt ceiling hostage). I'd argue he is leading but if Republicans won't follow, they can't be forced. The president is, by design, limited in what he can do legislatively. And certainly in how he can affect the economy.