How to replace elements from array with another element

I have a JSON array of objects out of which I need to create an Object of countries and continents like below:

For ex-

{
 "Asia":['India','China'],
 "Europe": ['Germany','United Kingdom']
}

So basically in above object continents would be a key and all the countries corresponding to that continent would come into array as a value.

This is what I want-

1. Unite Kingdom should replace with UK inside an object.

Below is my code but its giving a wrong output:

   const arr = [
         {
            'id':1,
            'geography':'region',
            'zone':'Europe',
            'countries':['United Kingdom','France','Germany']
         },
         {
            'id':1,
            'geography':'global',
            'zone':'global',
         },
         {
            'id':1,
            'geography':'region',
            'zone':'Europe',
            'countries':['France','Germany','Netherlands']
         }
        ];
        
const obj = {};

for(let i=0; i<arr.length; i++) {
 //Check if geography is region only
 if(arr[i].geography === 'region') {
    //Checking if property is already exists in object
    if(obj[arr[i].zone]) {
        obj[arr[i].countries].map((items) => {
           obj[arr[i].zone].push(items);     
        });
    }
    //If property is not there then insert
    else{
        obj[arr[i].zone] = obj[arr[i].countries];
    }
  }
}  

console.log(obj);

Its giving me below output:

{ Europe: undefined }

Someone let me know what I am doing wrong in above code.