perhaps not even the number of mass shootings, but the number of people killed in mass shootings
This is a common
feeling promoted by how he media report on "mass shootings", but it really is over stated, by a lot. Indeed, in a few cases, a so called "assault weapon" is used in mass shootings, and the media gleefully point to that. But in the vast majority of them, it's a 9 mm handgun, or similar, and the media don't say anything about it.
What the data says about gun deaths in the U.S. | Pew Research Center
Now, couple this with the hard fact that there is nothing uniquely deadly about an AR-15 that cannot be mimicked with another less dangerous LOOKING rifle like the one below that fires the same round, just as quickly, same muzzle velocity, same deadly final result.

And of course the proposed "bans" are broadly only on the sale of new "assault weapons", leaving millions of them out there. The most deadly firearm in common use is the 9 mm handgun, and that is used in most mass shootings (or maybe they use a 10 mm at times, but the 9 is most popular/frequently held.).
We had according to the above 61 mass shootings, using the most common definition, in 2021. I don't recall any involving an AR-15 type weapon, there could have been one.