D3 Choropleth map not displaying

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The map isn’t showing because you’re trying to select that empty g on svg that may not be there:

      svg
        .select("g")

You need to give it a class or ID when you create it and use the selector or append a new one (appending works). Next, since you’re using projected data (see above) you can’t use a different projection:

        .attr( "d", us_geoPath );

This has to be a plain d3.geoPath().