Wipe your phone. If more people do this before travelling to the U.S. it'll quickly become less "suspicious". This is a privacy issue. I don't have anything to hide, but I also don't like the idea of having the contents of my phone backed up and saved for 15 years. It's just like how there's nothing under my pants that is of interest to the authorities. I just prefer wearing pants.
Another good tip for travelling to the U.S. is to fly, rather than drive, and to do a TSA pre-check at your point of departure. That way, if the Americans get too paranoid, you're not trapped on foreign soil and subject to their whims. You can just cancel your flight and go home.
Better yet, don't travel to the U.S. right now unless you absolutely have to. It's not a good time to vacation there. Your country may have travel advisories in effect for the U.S. (mine does). Listen to them.