The “Shipping Calculator” can be enabled via the WooCommerce settings in order to give the user a way to calculate their shipping fees before getting to the Checkout Page. Usually they fill out the country, state, city and postcode form fields and click on “Update Totals” in order to calculate the shipping.
However, what if you only calculate shipping based on country? Or what if you only charge by zip code / postcode? In this case, you will need to hide the input fields you don’t need, and make UX better.
Well, here are some WooCommerce filters you can use from WooCommerce version 3.4 onwards to hide the fields you like (apart from country, which is mandatory).
WooCommerce: how to hide shipping calculator input fields