I’d like to say 100%, but some of the guns in America are Sig P320s, so almost 100%
This may shock you, but the picture below shows a rifle that is not only capable of being used in war, but was actually used in war.
A short magazine lee Enfield built in the early 1940s by a subcontractor of BSA (their factory was a little exploded at the time) and sold to the British army. It survived the war, and eventually made its way stateside, and into my hands.
Not only is it as capable of killing men as it was in the 1940s, it is chambered in a far more dangerous caliber than an AR-15s .223 (optimal for hunting coyotes, and small boars) the SMLE was chambered in .303 British (not in common use today, but great for deer, and small bears. You know, human sized animals) it’s actually illegal to hunt deer with ar-15s in some places because it is such a small, and underpowered cartridge that it would be cruel to shoot a deer with it, it doesn’t put them to sleep fast enough.
As for automatic weapons, there are 234,718 transferable machine guns that can be legally owned by U.S citizens. This number shrinks as time goes on, and unless the government changes laws significantly, will never go up.