The Shanghai Maglev isn't much more than a novelty at this point. Originally it was a somewhat useful way to travel to the airport instead of a bus, but now that the metro runs there that seems to be the better option (you don't have to deal with the maglev transfer or with buying another ticket). They had planned to extend it to Hangzhou, but the high speed rail between Shanghai and Hangzhou ended those plans.
Depends on what you mean by "panned out". The tech works, but society isn't interested in trains since it was developed and matured.
We pushed cars, freeways, etc. Not just in the US. Other countries followed along for their own reasons.
It's like nuclear; the tech can work fine. We just don't have the interest.
I blame lobbying against public utilities, personally. Decades of pro-privatization rhetoric, getting people to buy-in on their own vehicle, versus pub-trans.