This example displays the geographic boundary of the United States as a single dark green polygon with a red stroke on an aqua background, rendered using SVG. The code loads world country data from the World Atlas TopoJSON source via `d3.json`, converts it using `topojson.feature`, filters for the United States, and projects the path with `d3.geoAlbersUsa` and `d3.geoPath()`. The `geoAlbersUsa` projection is scaled and translated to center the map within the 960 by 500 pixel viewport.