What should a global publisher services company truly deliver?

I've been exploring what a publisher services company actually offers beyond just distribution and honestly, the more I research, the more questions I have. Reaching international readers sounds straightforward until you realize how complex it truly gets. So I'm asking those with real experience here which global publisher services company genuinely opened new markets for your book, and what did that worldwide reach actually look like in practice? Where do authors get misled globally? Honest experiences only, please.