Keep in mind too, that many animals were brought to the United States by explorers. The same may be true for animals in Australia. Some polar bears actually enjoy warm temperatures. And can survive in either warm or cold. This is intelligent design on Gods part.
Many cars have both heaters and air conditioners.
This is not because of Evolution, but because the guy who designed them was pretty smart. Knowing that some cars would be transported to warm and some to cold climates. Many animals that have specific diets, or temperature requirements may actually be the result of adaptations. We can t say that just because an animal only eats one kind of food today, that it always ate only that kind of food. It's an arboreal animal, with a highly specialized diet of eucalyptus leaves.