Snippet to change the default country and state on the WooCommerce checkout page. Supports PluginHive Shipping Plugins: https://www.pluginhive.com/product-category/woocommerce-plugin/woocommerce-shipping/

functions.php

// Change the default country and state on checkout page. 
// This works for a new session.
add_filter( 'default_checkout_country', 'xa_set_default_checkout_country' );
add_filter( 'default_checkout_state', 'xa_set_default_checkout_state' );
function xa_set_default_checkout_country() {
  // Returns empty country by default.
  //   return null;
  // Returns US as default country.
     return 'US';
}

function xa_set_default_checkout_state() {
  // Returns empty state by default.
  //   return null;
  // Returns California as default state.
     return 'CA';
}