In classes like the 470 and Finn without much national presence, it was pretty much an open qualifier. Obviously they had to restrict numbers for a large class like the Laser.
I think for the most part qualification was based on performance in various high-level regattas like the Miami OCR. I...
Currently in the US Sailing website, it lists Charlotte Rose for the Radial but nobody for the standard rig.
https://www.ussailing.org/olympics/teams/?gclid=CjwKCAiAleOeBhBdEiwAfgmXf2lDcHLT5NpDy7vjH-lnVh9e9zl--53WNxnqxL4N9vwf3FptyR4h3xoCHkwQAvD_BwE