Most USB 2.0 ports support > 0.5A in practice.
A key factor is the USB cable, excessive voltage drop due to high resistance will cause problems and excessive current draw.
Use the included USB 3.0 cable for testing.
We did a test and needed a very “heavy” USB device to come close to 0.8A. Using a more typical USB DAC (iDAC 2) we get around 550mA.
