China has returned the US naval drone it seized five days earlier in the open waters of the South China Sea -- and got a lashing by President-elect Trump on Twitter. Trump has already irked America's rival superpower by breaking protocol and speaking with Taiwan's President, challenging the "One China" rule, and talking about trade tariffs. Is the drone incident a test of an incoming administration bent on challenging China on trade, or a troubling sign of Chinese aggression in the South China Sea? Even some foreign policy experts skeptical of President Trump say it's high time Washington took a tougher stance with Beijing. So what does the incident tell us about the future of the US-China relationship with a Russia-friendly, unpredictable and confrontation-prone leader in the White House.