Do you really think Georgia disobeyed US? With 128 US employers on
official government positions in Georgia? With WHOLE Georgian government
officially monthly becoming salary from one of US "independent" fonds?
With about 300 (may be more, but 300 are official) US military advisors in Georgian army? Do you really believe Saakashvilli acted independently? US certainly knew about his actions and plans. After all, they mastered these themselves.
What is however not completely clear is if US ordered the attack at the exact moment or Saakashvilli just launched it a bit too early at his own risk with US government thinking "ah well, let him try".
Btw, i also think US seriously underestimated the rage and cruelty of Georgian nationalists and consequence of them entering S. Ossetia. Or may be not ... but i try to think good about americans