A long harsh digital trip - final meter?

How do you know the last meter isn't really the first meter?

If it was actually a single ethernet connection from the data source to your DAC, then it would be the last meter of multiple hundreds of thousands of miles, but in this case, the digital network connection is passing through numerous digital devices which buffer and reclock the data. Each of these removes some noise and anomalies from the signal and adds others. 

So in reality, each connection between every piece of equipment has it's own affect on the signal integrity and noise. 

In this case, the last meter doesn't even use the same protocol and electrical characteristics as the preceding hundreds/thousands of miles. USB has it's own issues compared to ethernet and the cable requirements are different. 

It's unlikely that the USB cable is going to affect the integrity of the digital data unless it or the two devices you are connecting have a badly flawed design. But it is more likely that noise and waveform integrity affected by the cable could influence the sound of the DAC. 

Whether it's worth spending $500, $1000 or more on a USB cable is up to you. While I personally believe that cables make a difference to the sound quality, I also believe in balanced investment. For example, I don't think spending $2000 on a USB cable to connect to a $500 DAC is ever going to make sense. I've generally found that, after a point, spending my budget on better electronics results in more improvement than spending a ton on cables. Where you draw that line is obviously a personal decision. 

I used to think USB cables did not matter. I can't remember the brands but I tried a few including "High Speed" etc....  To make a long story short, I went back to the best sounding one, a very thick well shielded cable that came with a printer for my office 10 years ago. It sounds simply wonderful and I have no idea what it is. The moral of this story is that every cable matters. I could hear the difference even when wanting the new cables to sound good.  If your system is resolving, and you listen well, you will figure out what you like.  

"So I guess it’s possible to truly transform and correct a digital signal during a very short journey thru a usb cable?"

No. 

It's possible to truly transform and destroy a digital signal during a very short journey through a USB cable. 

Many here do so with great flair and hubris.  :) 

Buy a Jcat ethernet Femto card for PC 
for a Substantially cleaner digital signal ,and isolation from 
the Noisy computer environment .