I’m not sure about US law but even in the UK and Europe these sting operations are used.
A common one is to catch bicycle thieves; by leaving an insecure bike in a place with a tracking device. This also happens with motor cars similarly trapped (often to lock the offenders in the vehicle on central locking!)
There are also the undercover stings of drug dealers.
I think the way they are used is different though. In Britain, the cops are not attempting to entrap randoms; they already know who they are after and have set the covert operation up in one of their normal areas where they operate.
Under UK law cops can arrest people anyway on suspicion of drugs posession or theft; and use this operation as part of wider evidence-gathering – and also so they have a reason to search other places where stolen property or drugs may be being kept (if someone is busted for small posession their house can immediately be searched). Petty thieves, robbers and addicts who do crime to pay for their drugs tend to prey on the same areas.
If you look at the press releases after this sort of operation it seems that randoms/first timers (particularly if they are young) are usually just arrested and cautioned or even released without charge but given a warning.
TBH I think the main reason for this sort of operation isn’t even to catch that many hardened criminals but to frighten younger people and opportunists away from blatantly breaking the law in public places..
