I have a Land Cruiser 2010. It's the third time this is happening. Any USB stick that's connected to the Audio USB/AUX port gets super hot and stops working after a few seconds. Yesterday I connected a bluetooth receiver in this port as well and it was killed the same way. I'm sure this USB port is for music and not charging as its right next to the AUX port.
Any idea why this is happening and how I can prevent it?
The port is badly broken, stop using it until you get it fixed.
If it has always been like this, chances are the port is miswired so that the +5V and ground pins are swapped (perhaps an internal cable plugged in the wrong way round). The reverse polarity would almost certainly destroy any devices plugged in (there's no way to plug in any USB connector the wrong way round, so this is not a risk that device designers would normally protect against).
On the other hand, if the port used to work normally and then started doing this all of a sudden, it's fairly likely the USB hub powering the port is toast and its 5V regulator is potentially letting full 12V+ through. Such an excess voltage will likely fry any unsuspecting device. The only solution would be to have the USB hub inspected and replaced. (Which might entail replacing the whole entertainment system or something, I'm not familiar with the car.)
If you have a multimeter, you can check what is going on. Find an old usb cable you have lying around, and strip it until you get 4 wires. Then, find which wires are 5V and Ground by using the continuity test and a usb pinout online.
After you have identified these wires, plug the cable in and test the 5V and Ground wires with the multimeter. If it reads a negative voltage, then the USB socket in the dash has incorrect connections to the car's wiring harness, and the socket should be removed and repaired, or it should be replaced. If the voltage is over 5.5v, then you need to replace the voltage regulator.
Alternative solution, fill the port with hotglue to prevent anyone using it in the future, and use a cigarette-lighter to USB adapter for charging things.
You could just tape over it, but that's not as secure and may fall off.
Downside, this won't help with reading the USB disks for audio, but you'll stop frying devices.
This assumes it's the power source only, not the data lines being out of spec, but...
Take a USB extension cable (shorter one; non-active), and carefully cut only the outer sheathing somewhere along it. Cut ONLY the red and black (usually those colors, ymmv), and wire them to a separate USB A plug. Power the device from a cigarette lighter socket adapter instead of the radio.
Alternatively, spend thousands upon thousands of dollars to replace the media center radio.
