While what you're saying is in general true, armadillos are a different story (specifically the nine-banded armadillo, the one you're talking about). They've been steadily expanding their range for a hundred years now, ever since they crossed the Rio Grande in the late 1800s and were introduced to Florida around the same time. They've been spotted by now as far north as Illinois, and it's expected that they'll go almost all the way to the Canadian border before they stop.

In part that's because of climate (armadillos can't survive consistent freezing temperatures), but they would have spread that far no matter what. They could have lived in Tennessee a hundred years ago if they'd been introduced there, it's only that it's taken until the last 20 years for them to get a population foothold there as they've expanded. The primary reason for their expansion is more that they don't have any natural predators in America, so they can go wherever they please. So they're slowly filling up space that can acommodate them, and which could have done so all along.

However, while I don't think the armadillo fits the profile, there definitely are examples of animals responding to changes in the Earth's overall and regional temperatures. Moths in Borneo have been moving uphill because it's getting warmer. Pikas in North America are unable to survive in environments that are too hot, which is why they live in mountains, but they've been moving uphill as well, to escape the shifting temperatures that make the lower slopes of mountains inhospitable to them.

Marmots are going into hibernation about three weeks earlier than they used to. Polar bears are hit hard too, and not just the dramatic ones that drown in the ocean during nature documentaries—it has to do with the fact that polar bears fast during the summer when the ice is too far away to reach, surviving on their body fat in a sort of walking hibernation, and the ice has been leaving earlier and returning later, meaning the bears have less time to build up fat through hunting and at the same time need to survive longer in the summer on that reduced body fat. This also means that the polar bears are more likely to enter human areas in search of food or refuse, which makes it more likely they'll get into confrontations and be put down.

The red fox is moving north, some species of squirrels are breeding earlier (which is triggered by temperature), the size of coral reefs (which is a type of animal that thrives in shallow, warm water) are increasing, sea turtles are breeding earlier, barnacles are moving north, so are some types of fish, plants are blooming earlier and some types are doing better than they used to because of more warm areas.

While people can argue all they want about the reasons for climate change, it's fairly clear that there is a change, and the animal world is responding to it. Some species adapt better than others, which is a foundation of evolution. We shouldn't think that we can keep everything exactly the same as it is right now, or even that we should try, because change is part of life in the wild. But most natural changes happen slowly, and even if what's going on now is a natural change, I feel that we are contributing to it and speeding it up with everything we pump into the atmosphere. The faster it goes, the harder it is for species to adapt and the more likely it becomes that we will be at least partly responsible for the demise of some. That's nothing new for humans; we're practically our own walking, talking extinction event for the animal kingdom. But it's a shame, and I wish we'd take it more seriously.

Anyway, I just wanted to say that you're right that animals are responding to a generally warming planet, I just wanted to note that the rise of the armadillo is following a similar trend but for a different but sort-of-related reason. Seriously, soon enough USA is going to stand for the United States of Armadillo.