Get Cart Items by User ID

function wc_get_cart_items($request){
	$user = array();
	$email =  $request["user_email"];
	$user = get_user_by( 'email', $email );
	$userId = $user->ID;
	$saved_cart_meta = get_user_meta( $userId, '_woocommerce_persistent_cart_' . get_current_blog_id(), true );
	return new WP_REST_Response($saved_cart_meta['cart'], 123);
}
add_action('rest_api_init', function () { 
	register_rest_route('wp/v2', '/cart_items/', array(
		'methods' => 'GET',
        'callback' => 'wc_get_cart_items', //Function name
    ));
});

Parms –

user_email = XXX@xxx.xom