Well, it was a slow process of decline. The peak of greatness was somewhere from 1945 to 1960. Everybody bought American cars, "Made in America" meant quality and a lot of things were made here, we won wars and they were usually declared by Congress (Korea being an early exception), Hollywood made films that were great and not filled with cursing and graphic sex and violence, people respected the flag and authority, drugs were so taboo that people didn't dare mention them in casual conversation. America was respected all over the world. People didn't expect handouts and all sorts of freebies from the government. School kids recited the pledge of allegiance.
Is America still great? Yes. But that greatness is greatly compromised by the leftist agenda and cultural degradation, globalism, and other destructive forces.
In other words, it was the jews.