Their point about how other countries will take the US's stance as a cue is somewhat scary. If you try and cross any border it will be relinquishing access to all accounts. I'm assuming email also comes along with 'social media', since communication is by its definition social. So how do you protect yourself? I think just going with "Don't have any social media" isn't a good answer because the relationship that child…
Have all expected social media, with expected contacts (family, friends, colleagues, etc) and activity. But carry disposable stuff, because you can't trust it after it's been taken for inspection. If asked, just say they you're worried about theft ;) Or if you're on business, that it's your employer's policy. Which it should be.
For anything that you want kept private, be very careful to compartmentalize it from your meatspace identity.