There is data on gun use in the U.S. Unfortunately, we don’t have good access to it, which makes informed discussion almost impossible.
The Bureau of Alcohol, Tobacco, and Firearms collects statistics on gun sales and where those guns wind up. They know the make, model, and details of guns used in crimes throughout the country, where those guns were sold (or stolen), and many other data points. They’ve got background check data from gun sales. However, because of the Tiahrt Amendment, most of that data is unavailable to citizens — or even, it appears, to police forces.
That’s a ridiculous situation. You can’t have an informed policy debate when an entire category of highly relevant data has been locked away.