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Even if America went 100% nuclear in the 50s we'd still have gas powered vehicles and other CO2 emitting sources. Nuclear power plants would basically remove all the CO2 caused by heating and cooling our homes,which is a big chunk of CO2 emissions but not all of them. We'd be in a better spot than we are now but we'd still have climate change.
We need a multi prong approach to climate change that gives us green energy alternatives for all aspects of our lives.
It’s weird how concentrated efforts by all the worlds governments might actually affect the climate.
But I’m sure there are no lessons to learn from this. >

It was easy to all get together and agree to use alternative refrigerants and aerosols, when cost effective alternatives were really available. It didn't require any significant change in lifestyle or cost for the average consumer. It was easy
Stopping the use of hydrocarbons, on the other hand... >

Not entirely. 
There were options for years. Nuclear could have replaced coal and gas plants. Yet, there was a very strong opposition to nuclear by both environmental activists and the oil/gas industry. We sought a 'perfect' solution, rather than a practical one and it paralyzed us. 
It didn't help that politicians kept rolling over backwards for the oil and gas lobby