Here in MA they call it a townhome if it is one verticle section for one family and then another for another family. It's a duplex if its like you living on the bottom floor and someone else on the top. We do have row houses in Boston but they are pretty uncommon everywhere else and I don't think many have been built since like the 1890s. Rowhouse to me is more like a whole block being just one connected row but technically it is all separate lots just with walls touching. Really common in like England.I rented a Townhome for a year, there was 4 to 6 foot between the houses at some spots, but never heard the neighbors at all. Of course it was a quiet area, and no one was having parties with loud music, so that would probably make a difference.
Do they call the buildings that share walls, Townhomes in other parts? We always called them duplexes or row houses (not that I have seen row houses in Texas).
Townhomes are really popular for builders here, they sell for maybe 75% -80% as much as the single family houses of the same square footage and they can cram two on a lot, which is important when even a .25 acre lot with no improvements is worth 400k+. Everyone I know prefers single family but the only single families that get built are 3k+ sqft and going to 1.2-1.5M min or you buy a 60s ranch, probably as much per sqft as the townhome, and deal with an older home.