In looking for information related to my ny-power demo (which shows the realtime CO2 intensity on the New York power grid), I discovered Electricity Map. This is doing a similar thing, but at a global scale. It started primarily focused on Europe but is an open source project, and has contributions from all over the world. I helped recently on some accounting and references for the NY ISO region.
You'll notice a lot of the map is grey in the US. That's because while most of the public ISOs publish their real time data on the web, private power entities tend not to. It's a shame, because you can't get a complete picture.
What also is notable is how different the power profile looks like between different regions in the US.
It's also really interesting if you take a look at Europe
Germany is quite bad on it's CO2 profile compared to neighboring countries. That's because they've been turning back on coal plants and they shut down their nuclear facilities. Coal makes up a surprisingly high part of their grid now.
The entire map is interactive and a great way to explore how energy systems are working around the world.