How to validate country?

Hi, i am trying to build a simple registration form which includes a select with country list like this

    <select id="country" class="form-control" name="country" required>
<option value="Afghanistan">Afghanistan</option>
<option value="Albania">Albania</option>
<option value="Algeria">Algeria</option>
<option value="American Samoa">American Samoa</option>
<option value="Andorra">Andorra</option>
<option value="Angola">Angola</option>
<option value="Anguilla">Anguilla</option>
<option value="Antartica">Antarctica</option>
<option value="Antigua and Barbuda">Antigua and Barbuda</option>
<option value="Argentina">Argentina</option>
<option value="Armenia">Armenia</option>
<option value="Aruba">Aruba</option>
...

I can't find a way to validate this in User model, i tried to inject something else as country and it works.

here's my registration controller validation part

    protected function validator(array $data)
    {
        return Validator::make($data, [
            'name' => ['required', 'string', 'max:255'],
            'lname' => ['required', 'string', 'max:255'],
            'country' => ['required', 'string', 'max:45'],
            'address' => ['required', 'string', 'max:100'],
            'email' => ['required', 'string', 'email', 'max:255', 'unique:users'],
            'password' => ['required', 'string', 'min:8', 'confirmed'],
        ]);
    }

I was also thinking about putting all these countries inside one array and try to compare it to the data received in controller like so, but have no idea where to put it

$countries = ['us', 'am', 'ru' .... others] 
$country = $data['country'];
if(!in_array($country, $countries){
return false
}