Not really.
At most, a USB isolator may help in some situations when galvanic isolation isn’t built into the DAC, but what I’ve seen is that you may make things sound different by exchanging one set of jitter for another. That is, you can see the jitter signature change, but rarely is it "better."
DACs made in the last 10 years have fabulous jitter elimination built in and USB asynchronous is usually the best. Also, old DACs performed remarkably better with high frequency signals than they do now. That was another reason to consider an extra external devce, like a sample rate converter like the Wireworld Remedy. Works wonders on old DACs but not really helpful anymore.
The only real use I can imagine with a modern DAC is if your DAC lacks asynchronous USB or streaming. Another possible benefit would be galvanic isolation which, ODDLY, not all DACs have built-in, like these:
USB isolation can be really helpful when streaming directly from a PC.