The dragons are much too weak as they are represented in skyrim. If one measly person can bring one down, even without using the thu'um, then how is it going to stand agains an entire country's army force. They would have to be very well plated to withstand bullets and explosions. Even with this, we could probably easily capture and contain them. We would also have to develop ways to fight against the fires that would inevitably spread.
Although I think a bigger problem is seeing a gigantic friggin frosbite spider has made a home out of your home. Just saying, I'm scared of the current size of spider. If they grew that big, I would just live in a titanium box, hidden away from all of them. Not including draugr or trolls or vicious sabre cats. With everything that prowls the landscape of Skyrim, we'd need to be very cautious of the wild.
I definitely think that a lot of things would be replaced with our powers of magicka. We wouldn't even need to use fuel anymore, since we could just power electric cars with a bolt of lightning. if we were cold, we'd just heat our hands and hug ourselves. I think alot of problems would be solved. Although, a lot of kids would now have a lethal weapon at their disposal at any time they want.
Indeed, our world would be much different than what it is now. Even religion, which in game has undisputed proof that the aedra and daedra exist. There'd be no more religious wars, how great would that be. Except the damned Thalmor, of course.
Hopefully something in this heaping mess of words entertained you. Either way, thanks for sticking through it.