A few Mac OS versions ago. I think it was Mavrix, I couldn't play my purchased iTunes movies on the Intel Macs for some apparently obscure reason. Scanning various answers provided by Mr Google, I began to suspect the DisplayLink USB graphics drivers. After locating the saved installer .dmg file, I uninstalled the drivers & my problem went away, along with it the ability to connect an external display via USB.
Earlier today, I thought I'd check whether there was an update to the DisplayLink drivers to suit Sierra. There were. Downloaded & installed, works fine.
My Intel Macs either lack Thunderbolt completely or have only one T/bolt port, so if I have that port in use with an ext HD, I can also use an external display. My T/bolt SSD/HD adaptor doesn't allow daisy-chaining as it has just one T/bolt port.