Google serves the world as their customers. It seems to me that having a preponderance of US-based employees that's wildly out of proportion to their customer (or revenue) base is still heavily in favor of US workers.
Many large companies serve the world (Xiaomi, Hikvision, Hitachi, Samsung, Mitsubishi..) while their employees in their home countries are overwhelmingly native. So if international customer bases are the norm, but only Google (or US companies) have significant international hiring, that effectively disfavors US workers.