Well, they’re not killing each other, just being the perfect communists ants are :-)
Their behavior, based on their origin, is probably associated with the “tweak” in their living environment being this far north. If you look at an individual ant as the carrier organism for a subroutine of a larger self replicating program, that subroutine is having troubles meeting some of it’s necessary requirements in the form of variables in something like temperature, moisture, or nutrient sources.
I.e. There may be a certain temperature need for satellite colonies that also must fit into a moisture range that isn’t found often in the tropics, but happens to ideally occur in the confines of an electronic device up here.
It will take that kind of approach to noodle out a solution to efficiently terminate colonies, or finding something in south America that happens to be endemic there that keeps them in check but doesn’t do something odd here like make chickens feet fall off...