This example displays a map of the United States with circles representing the population of various cities, colored in blue to contrast against the teal state boundaries. Using the `geoAlbersUsa` projection from `d3`, the map renders state outlines and interiors via `geoPath`. A `scaleSqrt` function maps city populations to circle radii, while React manages the application state and loads both the US Atlas TopoJSON and city CSV data. The visualization highlights population distribution without explicitly referencing AQI values.