A US map displays state boundaries in light green with small red circles marking county centroids, computed via `d3.geoPath` and `d3.geoCentroid` from TopoJSON data. The visualization uses D3 v5 and the `geoAlbersUsa` projection, rendering SVG shapes. County population and COVID-19 case data from a CSV file determines circle sizing, though the visible circles have a fixed radius. Zooming is enabled through `d3.zoom`, and the map is drawn from the us-atlas counties-10m.json dataset.