Rec league hero here.
I call out USSSA bats all the time. Probably catch 3 or 4 a year. I used to think it was a big deal like OP, but after the 7th or 8th time I stopped caring.
Now if I see an illegal bat I'll just roll the ball to home plate, walk off the mound, and politely ask the ump if we can check that bat for an ASA stamp. They look, don't find anything, and penalize the cheaters for using it during an at bat.
The other team usually makes a scene and thinks I'm a douche, but most of the time it's just for show. In my experience, 9/10 teams using an illegal bat are seasoned dbags who think they can take advantage of teams who don't know better. Hell, I called a guy out for using an Ultra 2 in coed. He made a scene and acted like he was getting robbed, had no idea it was illegal, etc. Then in the parking lot when I asked him, he just says, "Yeah, I knew what that bat was." WTF??
Think about it, nobody stumbles onto a 454 Legit or any other elite utrip bat at Walmart or Sports Authority. The fact they even own the bat means they either went online and read the blurb on SBF, egay, etc. where it blatantly says "NOT APPROVED FOR ASA PLAY" or they have a friend who did the same thing.
Bust the cheaters. You could be saving someone serious injuries, and you're keeping the game from turning into a circus.
If they don't know it's illegal they will now. Ignorance isn't an excuse to cheat. Learn the rules if you want to play the game, and if you do know the rules and cheat anyway then you deserve every penalty there is.