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?
I can't imagine it looking too different from climate denial, covid denial, or imperial decline denial. People will demand evidence of the forest and complain that all your samples are tainted with trees.
Maybe the coping would be more intense with the clear six-month deadline, but that's it I would think