If you look closely when walking around a neighborhood of row houses you'll find that they don't actually share side walls. Each row house has its own exterior walls with siding / exterior finish that may end up directly adjacent to the next house's exterior wall. This is apparent in areas where one row house has been torn down or is larger than its neighbor. Of course sound and fire might travel through these more easily but they share no structural elements.
For an example of what I mean, take a look at SF's Outer Sunset district on street view.
Edit: it's possible that terminology and construction methods vary a bit between cities so all I can say is that you can certainly build a row of houses that share no structural elements.
I would call those townhouses, it's probably just a regional thing.
The row houses I'm thinking about are in Philadelphia, and I think most other east coast cities. Occasionally you'll see one with the neighboring house(es) demolished, and there are usually remaining bricks from the missing house on the now exterior wall.
Has anyone built a new rowhouse, like those in Philly, since the end of WWII? Serious question. I don't think they are allowed anywhere in the US anymore. Existing ones are grandfathered in.
For an example of what I mean, take a look at SF's Outer Sunset district on street view.
Edit: it's possible that terminology and construction methods vary a bit between cities so all I can say is that you can certainly build a row of houses that share no structural elements.