It's a part of
American culture in many ways to have something of an obsession with the weather. In many countries, notably those to which technical support has been outsourced, people in contact with Americans have noticed this. Saying, "Can you believe this weather?" in response to a loud thunderstorm is a little like asking someone outside of the US, "Look at this, I've got legs! What's this sort of ambulatory thing they keep doing?" Many Europeans, Asians, and
Africans are confused by this.(I'm not sure how South Americans react) How can they go on about the weather all the time? Why? What's so incredible about American weather?
The source of this fascination is, in my mind, the newness of America to so many Americans. Most Americans have some immigrant blood in them. Many are only 2 or 3 generations, I happen to be, technically speaking, first generation as my Father is European. Because of this, the shock of moving to a new place is still rippling through the collective consciousness. The French and English and early American settlers who first landed in Kansas got to see their first Tornado, they saw the wind ripping apart fields and farms and houses. Amazing. Early Floridians and Spanish settlers in Mexico noticed that every late summer their beaches would be assaulted by gigantic storms. Dios Mio. If you've never seen a lightning storm send ripping torrents of static electricity into cornfields across Middle America in full view, you are likely to find it quite impressive. Furthermore if you are a farmer, the weather plays an important part in how likely your livelihood is to exist in two years.
Now, it has been a while since America was founded and settled, but despite this our parents, grandparents and so on still experienced this. And many of us move about the US to get away from cradles when we reach adulthood. We are a culture that seeks new things every other generations, often in new places. Sometimes it brings us to places with weather systems that are entirely different. The US spans a continent. It contains a rain forest that spans up to the arctic circle, a deep hellish pit of desert so far below sea level that evil parents in the southwest use it to torture small children, a vast and vibrant plain, two and a half ranges of mountains. And two coasts full of people to notice the land being battered by the sea. No matter where you go, you'll find interesting weather systems, at least for the first seven or eight generations that your family spends there. But then they're just as likely to bounce off to some other local.
So, it's really not all that surprising that Americans are so obsessed with weather. It's always new to them.