Apparently they refused entry to, detained, and searched people wanting to go to the protests in DC yesterday. So just wait until an event like that happens again, which is likely to be fairly frequent now.
The last time I even came near to, but not into, Canada via train, the train was stopped and heavily armed and body-armored CBP came on board to demand customs documents from everyone, including citizens not leaving the country during their trip.
My Dad has a mailbox for American packages just across the border, they seem to have quotas as his car is searched fairly regularly (it isn't a busy crossing).
