If you're old enough to remember the early 90's, the discussion about how/whether CD transports differ will be ringing bells . . .
It wasn't generally understood initially that there was anything more to the transport than delivering bits to the DAC: therefore they should all sound the same. Bit by bit (pun intended) it became more widely known (as it was in pro audio for years) that vibration, EM/RF interference and power supply ripple/noise all affected the performance of the DAC and even amplifier. Partly this was because these factors influenced the performance of the SPDIF clock, which is extremely sensitive to its environment.
The best CD transports produced demonstrably better sound by very careful engineering and seriously up-market clocking.
Fast forward to the computer age, and we're dealing with all the same issues: everything about the local playback environment of the DAC and amplifier change the way it performs, and even async USB DACs seem to be sensitive to timing, filtering and processing imperfections.
We've lost the spinning optical disc, but gained hard drives, with powerful neodymium magnets and three spinning platters: they're at least as 'toxic'.
We still have SPDIF - which still means the need for a very well implemented master clock driving the bistream - but now we need two clocks to handle all 44.1 / 88.2 / 176.4 and 48 / 96 / 192Hz sample rates. Often, these are low-rent devices in the worst possible place: attached conductively to the maelstrom of high frequency noise inside the laptop or desktop case.
Instead of beautiful high performance power supplies, we're using the cheapest, nastiest type imaginable: very much not designed for attachment to an audio system. This even includes battery-powered laptops, which derive most of their required voltages from grotty switching processes - and have monitors attached.
Then there's a world of interaction between the hundreds of threads and dozens of processes your computer is running in the background right now, that create impossibly complex patterns of electrical noise . . . all of which ends up hurtling down the 5V rail embedded in your USB cable, right into the heart of the DAC.
So yes, computers sound surprisingly different: in fact, they have far greater potential to screw things up than any old-school disc spinner. I would strongly recommend auditioning a few different computers to check this out for yourself.