For purpose of discussion, assume that due to bad luck, this asteroid has evaded the detection of all amateur and professional astronomers until about six months from impact. The asteroid is too large to deflect with humanity's current spacefaring capabilities, and the general scientific consensus is that the impact will end all multicellular life on Earth.
What do those six months look like?
The most unbelievable part of Don't Look Up is both the Chinese and Russian space programs failing to do anything while America can.
I thought it was implied the US sabotaged them
Correct.