As far as I recall, the LG Optimus G Pro has USB host. Most phones don't have settings anymore to enable it- it's simply always available. Once you plug in a USB host OTG cable and a peripheral it activates. The new LG G2 even pops up a selection of likely apps that are appropriate to the device you plug in.
It is odd that your car would want this feature since MP3 players never have USB host. Certainly iPods don't, nor do Samsung and Sony media players. The car usually acts as the host for the (client) media player.