Weak = danger
The patter of the media, consistent as always, is that Karzai needed a talking to because of corruption, that is all his fault. Played down was the visit by Ahmadinejad and his red carpet welcome by Karzai, and Karzai's trip to Beijing. But it's easy to imagine that Karzai making cozy with non-NATO foreign leaders is the real concern in Washington, and the real spur to drive Obama on his visit.
Obama's political weakness, and the health care bill did nothing to hide that from all but the most sycophantic supporters, is continuing to erode the remnants of Bush era policies. Since Obama is unwilling or unable to enunciate anything new, a more fluid diplomatic environment is to be expected.
Weakness is dangerous, especially when a weak leader is fighting wars, threatening new wars, and having his country's closest allies threatening to start even more new wars, while humiliating the leader's emissaries.