I know that generally speaking everyone traveling to the US from abroad have to pick up their luggage, go through customs with it, and then check it in again for their next flight. But is this also necessary when traveling on a precleared flight from Canada?
In my experience of flying from Vancouver, B.C. to the US I handed my luggage over basically to the TSA in Vancouver and picked it back up again when I reached my final destination in the US (which included a change of planes in Chicago)
No, if arriving on a pre-cleared flight and having a connection in the same booking, you don't need to pick up luggage, as you'll already have cleared customs, which is the reason for you otherwise needing to pick up the luggage.