While that's traditionally been true, my understanding is that most US streetcar systems are built with about the same specs as light rail, since that allows more flexibility in vehicle selection. I've sort of assumed all along that any "streetcar" we get will probably just be using single Siemens S70s as their vehicles, since that offers more operational flexibility.Isn't the "beauty" of a streetcar system that you don't have to do as much prep for laying rails. The cars are much lighter than LRT and there should not be the need to move any underground utilities. They should be able to do the line in considerably less time than an LRT line with less disruption to the rest of the road.
Everybody likes the little streetcars they use in Portland, but they violate Buy America, and they've apparently been hard to get parts, bad production timelines, etc. Streetcars require so few vehicles, and there's so few streetcar systems in the US, that there's not much compliant rolling stock available here, so it's cheaper, easier, and a safer decision to just use single LRVs.