Geo circle

<!DOCTYPE html>
<meta charset="utf-8">
<style>

.stroke {
  fill: none;
  stroke: #000;
  stroke-width: 3px;
}

.fill {
  fill: #fff;
}

.graticule {
  fill: none;
  stroke: #777;
  stroke-width: 0.5px;
  stroke-opacity: 0.5;
}

.land {
  fill: #222;
}

.boundary {
  fill: none;
  stroke: #fff;
  stroke-width: 0.5px;
}
  
.circle {
  stroke: red;
  fill: red;
  fill-opacity: 0.2;
}

</style>
<svg width="960" height="960"></svg>
<script src="https://d3js.org/d3.v5.js"></script>
<script src="https://unpkg.com/topojson-client@2"></script>
<script>

var svg = d3.select("svg"),
    width = +svg.attr("width"),
    height = +svg.attr("height");

var projection = d3.geoMercator()
    .scale((width - 3) / (2 * Math.PI))
    .translate([width / 2, height / 2]);

var path = d3.geoPath()
    .projection(projection);

var graticule = d3.geoGraticule();

var EARTH_RADIUS  = 3959;                         // mean radius in miles
var radiusMi      = 5000;                         // radius to be drawn in miles
var radiusDeg     = radiusMi / EARTH_RADIUS * 90; // radius in degrees for circle generator

var circle = d3.geoCircle().radius(radiusDeg).center(d => d);

svg.append("defs").append("path")
    .datum({type: "Sphere"})
    .attr("id", "sphere")
    .attr("d", path);

svg.append("use")
    .attr("class", "stroke")
    .attr("xlink:href", "#sphere");

svg.append("use")
    .attr("class", "fill")
    .attr("xlink:href", "#sphere");

svg.append("path")
    .datum(graticule)
    .attr("class", "graticule")
    .attr("d", path);

svg.selectAll(".circle")
  .data([0, 10])
  .enter().append("path")
    .datum(circle)
    .attr("class", "circle")
    .attr("d", path);

d3.json("https://unpkg.com/world-atlas@1/world/50m.json")
  .then(function(world) {
  svg.insert("path", ".graticule")
      .datum(topojson.feature(world, world.objects.land))
      .attr("class", "land")
      .attr("d", path);

svg.insert("path", ".graticule")
      .datum(topojson.mesh(world, world.objects.countries, function(a, b) { return a !== b; }))
      .attr("class", "boundary")
      .attr("d", path);
});

</script>

https://d3js.org/d3.v5.js

https://unpkg.com/topojson-client@2