REST API Parsing Example

After trying a number of APIs I'm finding the only thing they have in common is that they are all different and, if they return multi-level results, will need additional manipulation to be useful.
Would it be possible to get an example of the sanctioned method to parse multi-level results?
For instance the URL below will load countries data...
https://restcountries.eu/rest/v2/all?fields=name;capital;currencies;region;subregion;population;area
...but if you map all the returned fields in the Create List Operation the 3 currency related columns will not import into the resulting view.
I built an intermediary PHP file (below) that takes the result and parses it in to a single level table. It works but it seems pretty clunky. What's the right way to accomplish this, I'm pretty sure I'm going about it all wrong.
header("Access-Control-Allow-Origin: *");

header("Content-Type: application/json; charset=utf8mb4");

header("Cache-Control: no-cache, must-revalidate");

$curl = curl_init();

curl_setopt_array($curl, array(

CURLOPT_URL => "https://restcountries.eu/rest/v2/all?fields=name;capital;currencies;region;subregion;population;area",

CURLOPT_RETURNTRANSFER => true,

CURLOPT_TIMEOUT => 30,

CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,

CURLOPT_CUSTOMREQUEST => "GET",

CURLOPT_HTTPHEADER => array("cache-control: no-cache"),

));

$response = curl_exec($curl);

$response = str_replace("}],\"name","}],\"country",$response);

$response = str_replace("[","",$response);

$response = str_replace("{\"currencies\":","",$response);

$response = str_replace("}],",",",$response);

$response = str_replace("},{,\"country",",\"country",$response);

$response = "[".$response;

curl_close($curl);

print_r($response);

?>