How do I drive change across the org without authority?

You have earned influence, and now you are meeting its limit: you can shape the room you are in, but moving the whole organization is a different weight. Without a title that forces compliance, you have to win people one at a time, and that is slow, patient work. Feeling the difficulty here means you are attempting something genuinely hard, not that you are falling short. Influence without authority runs on trust and on other people believing your idea serves them, not just you. You cannot push change through an org. You can only make it something people want to carry. That means your energy is best spent understanding what each key person needs, not perfecting your argument. Pick one change you are trying to drive and one person whose support would unlock others. Before you pitch again, sit with them and learn what they are worried about. Solve a piece of their problem and you gain an ally. Change spreads through allies, not announcements.