But there arent any cops running around chasing down UPS guys willy nilly on a hunch a package from canada has a few pills in it... nor is there going to be big lettering on the box "CONTAINS ILLEGAL DRUGS" with which to clue them in.
Although I agree that it's unlikely that the package would be detected en route to OP's house, and most likely it will arrive without incident, it is possible that it would be detected and if the drugs are illegal it's possible that the police will try to make an arrest. I'm not just pulling that info out of my behind. In fact that very thing happened to a coworker of mine. She ordered some prescription sleeping pills from an internet pharmacy and when they showed up a Fed Ex guy knocked on her door and asked her to sign for the package. When she did and took the package a cop came up and arrested her and it turned out that the Fed Ex guy was also a cop. Apparently they were doing some sting or whatever, cracking down on people who illegally bought drugs on the internet.
Someone I read about had been arrested when she had gone to the shipping office to pick up her package with pills. Clearly they have a way to detect packages containing illegal drugs and it's not a matter of cops chasing down UPS guys willy nilly.
Most people that commit crimes do not get caught most times they commit crimes but it is entirely possible that they will. It's a gamble. If you don't want to risk losing that gamble is best not to play at all no matter how unlikely it is.