Correct me if I'm wrong, but wasn't it the nuclear winter that was caused by the meteor that slowly killed off the dinosaurs and not the impact itself?
You're not wrong
but if I may:*PUTS ON PITH HELMET* Depends on where you are and your definition of slowly.
Nuclear winter was the final killer yes, but there were some other nasty effects too, one worth noting is the firestorm wave. Basically, if you ever had to look up/study nuke tests, you know that super-heated air can travel much farther than the part of the shockwave that smashes stuff. A super-heated air wave may only hit you for a second or two if you are a few miles, (or hundred miles if we are talking big space rocks) from the explosion. And be only a little hotter than an oven, but this is enough to start combustion.
As far as we can estimate, the K-E impact's firestorm could have reached half the planet- exposure to oven like temps for 1-2 secs probably won't kill you directly, but it could start forest fires in areas located
on the same hemisphere FIGGEN' EVERYWHERE
relative to the impact site.
And the extra ash/soot from the worldwide fires does not make the nuclear/volcanic winter any shorter. For the other side of the planet thing take longer, + you have the tsunamis, the earthquakes, large amounts of super-heated ocean surface could make really really really really really
bad storms. also ash kills ozone. not to mention that- I'm, trailing off now, sorry, Paleontology gets me excited.
One last thing to remember: Macduff's rock is 40% bigger; I can't say how much worse that would make it. but the PVN and GTA did get a few hundred million out of Vasuda Prime, and the GTVA got most of everyone out of Capella, so mass exoduses are nothing new and may have contingencies.
and as you said:
Both the UEF and GTVA have terraformation equipment so it stands to reason that they could greatly shorten the length of the nuclear winter or maybe even outright prevent it. And even if they can't, Humans still have the necessary technology to survive in such an environment or alternatively evacuate to other habitats, like Mars, some moons or hollowed out asteroids like the Gefs use.
Of course a flood of billions of refugees would cause a whole lot of new problems all over the Solar System, but also opportunities.
So, the only question at that point is how many people could they get off Earth and how long do they have to do so. ( DefCynodont119 is NOT a professional Paleontologist/Geologist/Planetary Physicist. [yet] So take everything I say with a grain of Salt/Halite/Sodium Chloride. )