Just got back from my second round-trip between US and Korea, carrying a P3A.
First time, on the way back into the 'States at JFK a US Customs agent wanted to check that I didn't buy the drone in Korea and went so far as to ask what I did with the drone there.
Second time, the Customs agents at JFK were busy chatting, letting everyone walk by unmolested, making me wish I carried more scotch back. But on the security line at Incheon when I was asked if I had any laptops or tablets I cheerfully said "no" and plopped the P3A box and my 35mm camera bag onto the scanner's conveyor. Then they checked the drone box twice for explosives and walked away with my boarding pass for a few minutes. Maybe it was the drone itself or maybe it was that I forgot about the iPad Mini that was in the P3A's case. Oops. Dunno. Don't care. Went basically OK except for a few minutes of "hmmm" at security.
I think I actually removed the iPad from the drone's case on the prior trip.
Funny, didn't get that much scrutiny on the way out at JFK where everyone has to remove their bloody shoes... [shrug}
Your mileage may vary!