The US side would nod their heads and says there was nothing to be done about it.
Which border crossing had those incidents? So those girls were on the bus with you, they came back crying, and you have no idea why? Is there more context here?
Just sort of to tie this in to current events, some guy just drove into Canada without stopping the other day: https://vancouversun.com/news/local-news/driver-who-skipped-...
Now by luck police spotted the vehicle in Vancouver and tried to pull it over.
If someone tried this sort of stunt going the other direction what do you think would happen?
So police in Canada can demand your unlocked phone at any point, not just at the border?
http://www.justice.gc.ca/eng/csj-sjc/rfc-dlc/ccrf-ccdl/check...
"The context of the search, and the activity that brings a person into contact with the state, can have an impact on the person’s reasonable expectation of privacy."
...
"The degree of personal privacy expected at borders, where travellers expect to be searched, is lower than in other enforcement situations (R. v. Simmons, [1988] 2 S.C.R. 495 at page 528; Monney at paragraph 34; R. v. Jacques, [1996] 3 S.C.R. 312 at paragraph 18).
The expectation of privacy is reduced in the school setting in relation to the responsibility of teachers and other school authorities to provide a safe environment and maintain order and discipline in the school (M.(M.R.)).
Prisons carry a decreased expectation of privacy (Weatherall; R. v. Conway, [1989] 1 S.C.R. 1659). However, the lowered expectation of privacy within a prison does not allow the seizure without a warrant of bodily samples taken as part of a medical examination (R. v. Dorfer (1996), 104 C.C.C. (3d) 528 (B.C.C.A.))."
That said I've travelled dozens of times in a multitude of ports of entries and the vast majority of people have no problem, they're not searched, they're not detained. I haven't seen anyone standing in front of me in line have a problem either. You can avoid 99% of the problem by being polite, answering questions truthfully, and treating the border guards with respect. Yeah, it sucks if they have a bad day and they're rude to you or they ask you invasive questions, just play along and be nice. You'll be fine. If you are suspicious or if you piss them off they will potentially make your day very very bad.
All that said, I think the land border between the US and Canada should just be open.
By the way, you can also go on vacation without a phone ;) disconnecting will make your vacation better!