Something I've yet to see any complaints about is what the US CBP is wanting to see on a phone or other device. Again, there has to be a reason for them to ask - they are NOT allowed to just scroll through the contents of a phone or other device to see what's on it 'because they can' - they will be looking for specific things.

My 1st guess is because the travelers documents such as ticket, hotel and tour reservations etc are there. Since these days more and more travelers don't carry hard copies of the documents the only way to verify them is via their phone or other device. For foreign travelers entering the US - something that is always asked is length of stay, return ticket and lodging info. Those are the basic things they will ALWAYS want to know and you should ALWAYS be prepared to give.

 Print them out and now no reason to look at an electronic device...

As for TSA screening - all they will want to see is that the device turns on. During the years of my travels that is ALL they ever wanted to see (Disclaimer: I am fully registered w/TSA and Global Entry programs). In the case of a laptop, they are happy as soon as the initial boot or login screen pops up. They just need to verify that the large, dense, objects in them are batteries & not explosives.