Small multiple line chart

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3.v4.min.js"></script>
  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
  	svg {
    border:1px solid #d0d0d0;
  }
  </style>
</head>

<body>
  <script>
    var numCountries = 10
    var margin = {top: 20, right: 10, bottom: 20, left: 10};
 		var width = 80 - margin.left - margin.right;
  	var height = 300 - margin.top - margin.bottom;
    var compareCountries = ["United Kingdom", "Norway", "Germany", "Canada", "Netherlands", "France", "Sweden", "Ireland", "Spain",]
    d3.csv("incomes.csv", function(data){
      console.log(data);
    
    var svg = d3.select("body").append("svg")
      .attr("width", (width + margin.right+ margin.left)*compareCountries.length)
      .attr("height", height + margin.top + margin.bottom)
      .append("g")
    	.attr('transform', 'translate('+[margin.left, margin.top]+')')

var filteredData = data.filter(function(d){
      return compareCountries.indexOf(d.country)> -1 && 
      d.cutoff ==='cop50';
       });

filteredData.forEach(function(d) {
		d.year = +d.year;
    d.val = +d.val;
      });
    
      var americaData = data.filter(function(d){
        return d.country === 'United States' && d.cutoff === 'cop50';
      })
      var incomeByCountry = d3.nest()
    	.key(function(d) {return d.country})
    	.entries(filteredData);  
    
    var yScale = d3.scaleLinear()
    	.range([height,0])
    	.domain([0, d3.max(filteredData, function(d){ return d.val})]);
    console.log(yScale.domain())
    
    var xScale = d3.scaleLinear()
    	.range ([0,width])
    	.domain (d3.extent(filteredData, function(d){return d.year;
       }));
    
    var yAxis = d3.axisLeft()
    	.scale(yScale)
    	.tickFormat(d3.format('$,'));
    var xAxis = d3.axisBottom()
    	.scale(xScale)  
    	.tickFormat(d3.format(''))
    
    
    
    var line = d3.line()
    	.x(function(d) {return xScale(d.year)})
    	.y(function(d) {return yScale(d.val)})
    
    console.log(incomeByCountry)
    
    var countries = svg.selectAll('.country')
    .data(incomeByCountry)
    .enter()
    .append('g')
    .attr('transform', function(d,i){
      return 'translate('+(i * width)+',0)';
    });
      
//     countries.filter(function(d,i) {return i === 0})
//     .append('g')
//     .call(yAxis);
    
//     countries.append('g')
//     .attr('transform', 'translate('+[0,height]+')')
//     .call(xAxis);
    
    countries.selectAll('path')
    .data(function(d){return [americaData, d.values]})
    .enter()
    .append('path')
    .attr('d', line)
    .attr('fill','none')
    .attr('stroke', function (d,i){ return i === 0 ? 'steelblue':'gray'})
    ;
    
//     svg.selectAll('path')
//     .data(incomeByCountry)
//     .enter()
//     .append('path')
//     .attr('d', function(d) {return line(d.values)})
//     .attr('fill', 'none')
//     .attr('stroke', function(d) {return d.key ==='United States' ? 'steelblue' : 'gray'})
//     .attr('stroke-width', function(d){return d.key === 'United States'? 3: 1});
//     })
    
//     line(filteredData)
//     	svg.append('path')
//       	.attr('d',line(filteredData))
//       	.attr('fill', 'none')
//       	.attr('stroke', 'steelblue')
    
//     svg.append("text")
//       .text("Edit the code below to change me!")
//       .attr("y", 200)
//       .attr("x", 120)
//       .style("font-size", 36)
//       .style("font-family", "monospace")
     });

</script>
</body>

https://d3js.org/d3.v4.min.js