How to build query for google bar chart in laravel?

My Database looks like this

id  | country_name | population | created_at
 1  | USA          | 2000000000 | 2020-02-04
 2  | China        | 2200000000 | 2020-02-04
 3  | Russia       | 12000000   | 2020-04-02

My Query look like this. I am just trying to build query but not getting result.Maybe there are some mistake.

public function barChart(){
         $countries=Country::get();
         $graphic_header=['Year'];   
         $countrydata=[];
         $actionDate=[];
         $country_name=[];
       foreach ($countries as $country) {
           array_push($country_name, $country->name);
           array_push($actionDate, date('Y', strtotime($country->created_at)));
           $actionDate = array_unique($actionDate);
       }
       $graphic_header=array_merge($graphic_header,$country_name); //Dynamic Header
       array_push($countrydata,$graphic_header);
      foreach($actionDate as $d) {
          $d = [$d];
          $d = array_pad($d, sizeof($graphic_header), 0);
          array_push($data, $d);
      }
      foreach ($countries as $country){
          $date = date('Y', strtotime($country->created_at));
          foreach ($data as $in =>$gd){
              if ($date == $gd[0]) {
                  $index = (array_search($country->country_name, $graphic_header));
                  $country_data[$in][$index] = $country->population;
              }
          }
      }
          return response()->json([
           'data'=> $country_data,
           ]);
    }

I am sorry I cannot put image of bar chart how I want to draw But I am getting Result like this

array:2 [▼
  0 => array:4 [▼
    0 => "Year"
    1 => "USA"
    2 => "China"
    3 => "Russia"
  ]
  1 => array:4 [▼]
 0 => "1970"
    1 => 0
    2 => 0
    3 => 0
]

But I want data like this

['Year', 'USA', 'China','Russia'],
 ['2004',  2000000000, 2400000000 , 194500000],