I realize a USB 2.0 port can only supply 500mA, but 3.0 should be able to supply up to 900mA. Based of the spec the requirements are 200mA @ 9V or 1.8W so that would be 360mA at 5V. Is there a requirement for the higher voltage then? The input range on the power connector does say 7-30VDC.
The current listing of the radio is the peak current avg. while it is transmitting. What you don’t see is the slew rate in which this current is required.
While a USB 2.0 port should be able to provide the required current, no all of them do. So to be safe, especially on laptops, use the external power source.