This example displays a choropleth map of the United States, showing state boundaries filled with a solid red color against a green ocean background. It uses D3 v4's `d3.geoPath` with the `d3.geoAlbersUsa` projection to render the map, and TopoJSON client to parse state features from the us-atlas states-10m.json dataset. The React framework wraps the SVG container, with styling applied via CSS.