I don't know if Walt's vision would have succeeded, but the USA has had many planned communities. Some were unsuccessful, others were very successful. Every city eventually has to evolve or end, so none of them are the same as when they were first built. It depends how one defines "success."
I did a search, and WOW! There are/were a TON of them wordwide. In some cases, a city burned down, so the government took to rebuilding in an organized fashion.
A number of planned communities have been built/funded by companies, so it isn't impossible Walt could have done it.
In the USA, planned communities date back to our very beginning: Jamestown and St. Augustine. Jamestown was semi-planned, somewhat a disaster, and funded by the Virginia Company. St. Augustine is even older. The original mission of St. Augustine was to eliminate the French colonization of Florida and it succeeded in that mission. Clearly it has evolved.
Anyhow, I just thought that was interesting. A few years back I saw a documentary about Jim Rouse. Many of his plans have been very successful, though maybe not quite as he originally planned them.