USB3 = United States big 3. Stop picking on the poor kid. There's no age limits as far as I can tell for posting here. You might even be sitting behind him/her one day while they fly you on holiday, or on an aircraft transiting his/her sector.
I must agree re acronyms though. The amount of them in new operating procedures/work instructions I get that I genuinely don't understand and therefor have to seek clarification on is rather large, and some managers just love how much smarter using them makes them sound.