Hey Canadians:
I just heard about two Canadian friends of a friend who were driving into the US
the border agents demanded they unlock their phones; the agents searched the phones, found anti-Trump stuff on one ...
... then confiscated that phone and neither person was allowed into the US
These folks weren't activists or anything -- the search doesn't appear to have been triggered by that
so, govern yourselves accordingly
@clive The EFF has an in-depth guide for travelers coming into the US.
Don't forget the 100 mile rule.