Can tracks managed with iTunes be input to this unit's USB sound card (audio interface)?

Yes.

Windows
At the "Execute file" dialog on the Start menu, input "mmsys.cpl" and press "OK". An audio settings window opens. At the [Sound Playback] audio tab, select "PIONEER XDJ-AERO". Input the signal to this unit's channel 1. Signals cannot be input to other channels.
*This cannot be used at the same time as an ASIO driver.

Mac OS
At the [Output] tab at [System Preferences] -> [Sound], select "Audio output device", then select "PIONEER XDJ-AERO" from the sound devices.

When the mixer mode is set to XDJ-AERO, the tracks are input to this unit's channel 1. It is not possible to input them to other channels. When the mixer mode is set to PC, the tracks are input to this unit's PreMaster channel.