It doesn't help to share state between the front and the backend. What apline.js really excels at is managing state on the frontend itself, especially for UI. For example, if you need to click on one thing that shows another thing, or you need to swap out ui elements it helps to make that easier.

For communicating the backend through using an api, or issuing async get/post or form submissions that is done pretty much the same as you would do it using html or javascript.