And coundn't they try to assimilate the links? (of course there is the issue of them getting through it)
From what I see, this is how it begins.
1) The Thing would begin assimilating other animals (insects,rats, spiders...). From what we know, it can't assimilate plants, so we will assume it can't
2) ASsuming the 'Thingified' animals don't decide to simply spread over the world to infect it, but remain in town, we will use Mc-ready research to remember how it said it would take 27.000 hours to infect the world (1125 days AKA roughly 3 years), although according to Questionable Research it would take roughly 3000 hours (but we will ignore the comic)... that's for the whole world, area 510 million km2 ... which honestly makes the largest city in America only 12,461 much more... edible
510e6 : 27e3 = 12e3 : x
The results is that it would take over the entire area, assuming it's on par with the biggest area... roughly 35 minutes as an high end! I don't think people will have enough time to contact and quite a few would leave the town to try to spread.
In the meanwhile, the Xenomorph would be likely still gestating. The drone might have kidnapped a person or two. If the person happen to be infected should have enough awareness of its body to try to remove the Embryo when infected by a Chestburster.
3) Now, we will assume the thing CAN'T Assume the Xenomorph. I will however assume they will TRY to do it with one. So
(Fight with the drone and one of the 'things' )
The thing, aware of the drone what with all the animals looking around and having people's intelligence, should at LEAST try to become big enough to try to absorb overpower the drone like it did in the prequel. Given its access to weapons, he'd likely brought something like a grenade launcher and such. The Xenomorph's main form of offense would be trying to tear the thing apart (which won't work for long). Here there are two scenarios
3.1) The thing successfully wounds the Xenomorph, which unveils its acid blood and the Thing's weakness to it.
3.2) The thing is overpowered and eaten. Due to its acids and its silicon based form, I don't think the Thing WOULD be able to assimilate it and figure it out. The thing would at least try to escape with its peaces to warn its brethen
4) Now both aware of their threats, either the Xenomorph tries to infect the Thingfied animals (and no clue how a 'Thing-O-Morph' would be, but I assume a Thing would try to remove it). The infected host would however survive the bursting unless the Thing-O-Morph were to eat it/melt it.
The thing, instead, would begin a hunt. If some space trucker found out how to 'deal' with the Xenomorph by making flamethrowers, I assume a town of 1148 people and several weapons can do something about it (it hsould have a police station). I doubt Facehuggers would be any threat as well.
Once located the Hive, they would at least try to plant a bomb in it. Or, worst funny case, assimilate all the biomass and turn into a giant Thing made of 1148 people and try to throw down with the Queen in combat (would be at least amazing/hilarious to see)
AND EVEN THEN, the Human Things could try to contact the military to carpet bomb the entire town or get more fodder to use and more weapons as a warning (This assuming the things who did not leave have not already assimilated a good chunk of it)
I give it ot the Thing