@Joachim Thank you! This right here is exactly what I needed:
/**
* enqueue scripts and styles
*
*/
function nr_load_scripts() {
wp_register_script('googlemaps', 'https://maps.googleapis.com/maps/api/js?key=XXX',null,null,true);
wp_enqueue_script('googlemaps');
}
add_action( 'wp_enqueue_scripts', 'nr_load_scripts' );