I'm looking for world maps showing countries from 1950-2015. Are there shapefiles, KMLs or GEOJSON files of these?
I think you should have a look at cshapes it...
"provides historical maps of state boundaries and capitals in the post-World War II period".
You can download a shapefile and query the data using the fields containing the year to evaluate how country shapes have changed over time. I found this website by first looking on the PennLibraries website.