Factory Reset Your Phone
When I travel to the US, I factory reset my phone prior to landing. That is recommended after a software upgrade anyway and I usually do updates when on an airplane as I have lots of time and can't use the phone regardless. That's the reason I give, if asked.
They can search it to their hearts content. It is unlocked, has no data and is without a password; search / image away. You are cooperating and it's the equivalent of carrying an empty carry-on bag. They can search all they like, there is nothing to find. They don't like it, but there is nothing they can do. I'm always polite, even in the face of idiocy.
When reset, there are no contacts, no emails and no software installed save Android itself. You are legally obligated to give US Border Guards passwords to any software, apps, email or encryption installed on your phone. You are in no way obligated to download and install apps to your phone or tablet, or sign onto a mail/web/social media account that is not active on your phone or tablet. How can you sign in, it isn't installed? I have few social accounts regardless and the few important telephone contact numbers I need are memorized.
When out of the airport, I sign into my Samsung account, and my phone repopulates with all apps and data in minutes on decent Wifi.
Biting the hand that feeds IT
