"TypeError: string indices must be integers" after reading from a JSON file

On line 14, this is not valid, given the input data: lons.append(cp_dicts['geometries']['coordinates'][0]

You need to update the loop along these lines:

for geometry in all_cp_dicts['objects']['capitals']['geometries']:

    lons.append(geometry['coordinates'][0])
    lats.append(geometry['coordinates'][1])
    hover_texts.append(geometry['properties'].get('city', ""))

Note that for some of the locations, the 'cities' key is missing in the json. So you need to handle that when populating the hover_texts list, as shown.

Also, the 'data' variable was not working with Scattergeo. Below is a suggested revision to the syntax

data = Scattergeo(
    lat = lats,
    lon = lons,
    text = hover_texts,
    marker = dict(
        size = 5
        )
    )