Beginner racers may purchase a one day Cat 5 license at the day of the race so you do not have to join USA cycling immediately. Another idea is if you want to take a smaller step into racing is to do a sanctioned hill climb. The one I did yesterday is a mass start hill climb and each race category went off at 1 minute intervals. It will give you some experience lining up and starting with other racers but the speeds are slower and the field breaks apart so it is pretty safe race. However, hill climbs and time trials do not count toward your Cat 4 upgrade.
Some hate hill climbs but they are a great way to work on FTP and climbing. I set a new 20 minute power record yesterday that I doubt I would have done without competition.