OTL, the incident faded into obscurity quickly, before being rediscovered in the 1970s, after which it became a fixture of American pop culture. Assuming it never occurred, how would American culture be affected? Would another UFO incident take its place (such as Kecksburg)? A lot of UFO conspiracies probably won't exist, like MJ 12, but others might replace them. The biggest impact might be on Roswell itself, which would remain an obscure small town.