This example displays a choropleth-style map of the United States, drawn as gray state boundaries on a dark background. It uses the geoAlbersUsa projection to render the states as SVG paths, with the geographic data loaded from the us-atlas TopoJSON file. The React component fetches the data via useData, converts TopoJSON to GeoJSON with the feature function from topojson, and passes it to Marks, which generates the paths using d3.geoPath.