USB live capture is now possible, currently the following Audit Records exist: USB and USBRequestBlockSetup.
To capture USB traffic live on macOS, install wireshark and bring up the USB interface:
$ sudo ifconfig XHC20 up
Now attach netcap and set baselayer to USB:
$ net.capture -iface XHC20 -base usb
To read offline USB traffic from a PCAP file use:
$ net.capture -r usb.pcap -base usb
Don't forget to set the -payload flag if you want to preserve the data being transmitted!