Is what I did considered an act of disbelief (kufr) that necessitates sincere repentance (tawbah nasuh) and expiation (kaffarah), and are 'Umrah and Hajj sufficient for atonement?

We hope that your daughter is among the martyrs, as the Prophet, peace and blessings be upon him, enumerated categories of martyrs, among them the one who dies under a collapsed building, and a car accident can be similar to that. The reward for good deeds reaches the deceased if it is dedicated to them, provided that you have performed Hajj for yourself before performing Hajj on her behalf. The cause of the accident is divine decree and destiny, and one must be content with that. What you uttered in a state of shock does not incur a ruling; because it was a mistake and forgetfulness, and Allah accepts the repentance of those who repent.