Explain why Autism is so prevalent in the USA, as opposed to the rest of the world ?
What makes you think the prevalence in the USA is so different?
"In South Korea, a recent study found a prevalence rate of one in 38 children, and a study in England found autism at roughly the same rate — 1 percent — in adults as in children, implying that the condition had gone unidentified previously, rather than an actual increase in its incidence."