Can't speak for everywhere but in Washington state almost anything sold as a scooter or moped in fact requires a full motorcycle endorsement, liability insurance, annual registration, etc. The cutoff for a motorcycle endorsement is a max 49cc motor or 2 brake horsepower, which excludes nearly everything sold as a scooter that I can find.

You are certainly right that in most of the US biking infrastructure is embarrassingly bad, hopefully if pedal-assist ebikes get more popular that will spur more investment in bike paths and separated infrastructure.