Custom price based on custom field

custom_price.php

<?php

// Save custom calculated price as custom cart item data
add_filter( 'woocommerce_add_cart_item_data', 'save_custom_fields_data_to_cart', 10, 2 );
function save_custom_fields_data_to_cart( $cart_item_data, $product_id ) {

        if ( CUSTOMER_IS_IN_US ) {

                // Set the custom data in the cart item
                $cart_item_data['custom_price'] = GET_PRICE_FROM_CUSTOM_FIELD;

                // Make each item as a unique separated cart item
                $cart_item_data['unique_key'] = md5( microtime().rand() );

        }
  
    return $cart_item_data;
}

// Updating cart item price
add_action( 'woocommerce_before_calculate_totals', 'change_cart_item_price', 30, 1 );
function change_cart_item_price( $cart ) {
    if ( ( is_admin() && ! defined( 'DOING_AJAX' ) ) )
        return;

    if ( did_action( 'woocommerce_before_calculate_totals' ) >= 2 )
        return;

    // Loop through cart items
    foreach ( $cart->get_cart() as $cart_item ) {
        // Set the new price
        if( isset($cart_item['custom_price']) ){
            $cart_item['data']->set_price($cart_item['custom_price']);
        }
    }
}