This is a familiar topic. Pretty much the only thing you can't find MUSA is shifting and tires ... and maybe saddles? You can get frames, hubs and other bearings, rims, spokes, suspension, some drivetrain, cockpit. But no one offers a build like this, it's all assemble yourself.

For mass market, Guerilla Gravity makes frames in the USA. There are lots of build-to-order shops. Ventana and Sycip are the ones local to me. Ventana was started by a man who was once a welder at my employer, and they often make frames for other brands when they're starting out.