Tip, I just upgraded to 10.13.6 and had an issue. Are you getting the message about /dev/cu.usb (or something like that, I'm not on that Mac right now to double check)?
What I found (after reinstalling drivers, etc.) was that I needed to open up System Preferences > Security & Privacy. When I did that there was a message (in the General tab) that some drivers had been blocked on boot. I can't remember the exact message, but I was able to click "Allow" or something like that and pick the drivers I wanted to allow - one of them was Prolific (for my cable) but there was like 5 or so drivers blocked and another was an FTDI driver (for Arduino stuff) - note, though, that FTDI was listed as "Future Technology Devices International" (which is what FTDI stands for).
So, it wasn't that the driver wasn't still installed, or that CHIRP wasn't working right, it was just that macOS 10.13.6 had blocked the driver (and others) and I had to explicitly allow them.
You might try rebooting if you don't see that in Security & Privacy right away. You might also try reinstalling the driver (instructions on CHIRP site) just to force macOS to show that option to allow the driver. The magic (I think) is in watching System Preferences > Security & Privacy (General tab) for any messages that macOS is blocking you and explicitly choosing allow when it does.
-Tycen K7TYC