Prepend a country code to the beginning of all URLs in WordPress

For this you would have to adjust the permalinks. You can control their processing e.g. here:

function my_page_rewrite() {
	add_rewrite_rule('^sa/([^/]*)/?', 'index.php?pagename=$matches[1]', 'top');
}
add_action( 'init', 'my_page_rewrite' );

In this case, a requested page with leading /sa/ in the URL will be processed. Of course, the permalink settings have to be saved again for this.

BUT: you would have to set these links too, of course, so you would have to adjust the permalink generation (and not only its processing) as well. And here I wonder how you want to do that with your construct?

Actually, you can also solve such language-specific settings with translation plugins like Polylang.

Hey threadi,

Thanks for your replay, your answer really helpful for me to find solution.

Following code works fine for me,

default url output:
https://www.website.com/shop

public static function rewrite_url() {
    global $wp_rewrite;
    $country = $_COOKIE['country']; // us or ca
    $wp_rewrite->root = "$country/";
    $wp_rewrite->extra_permastructs['product']['struct'] = "$country/product/%product%";
    $wp_rewrite->flush_rules();
}
add_action( 'init', 'rewrite_url' );

new url output:
https://www.website.com/us/shop
https://www.website.com/ca/shop