Due to the complexity of US taxes and many automation options (like Jetpack or TaxJar), we do not automatically add tax rates to new stores.
If you prefer manually managing your taxes, you can import the tax rates for each state from the WooCart US localization folder using WP-CLI.
Here's an example for Arizona:
wp-localize "United States" AR
The source for US tax rates is Avalara.
Please make sure to manually review all tax rates after import.