USB is no longer an option (sort of...)
...With the jump to version 4.x Ice Cream Sandwich, along with the switch from microSD to internal file storage, Android devices also switched from USB mass storage to the media transfer protocol (MTP). (The change actually happened in Android 3.x Honeycomb, but most users didn't really notice it until the Samsung Galaxy Nexus debuted later in 2011 without a microSD card slot.) The intent was to make Android devices more accessory friendly and to simplify file and storage management when connected to a computer, but the result was that MTP took Android/car USB connectivity from inconsistent to flat out unsupported.