This example displays two choropleth maps: global country-level and US state-level average temperatures, colored with a sequential RdYlBu scale. It loads GeoJSON features from TopoJSON files via `topojson.feature` and maps temperature data from a CSV using `d3.rollup` to compute means per country and city. The world map uses a `d3.geoNaturalEarth1` projection, while the US map uses `d3.geoAlbersUsa`, both rendered as SVG paths via `d3.geoPath`.