Short answer is that you do not, unless you have presence, defined as nexus in the US.
You can read yourself in the many cases you are considered to have nexus from this source: https://www.webretailer.com/lean-commerce/us-sales-tax-ecommerce/
The definition is quite wide and varies between jurisdictions.

If your main business will be in the US, my advice is once you get high US traction, to get a local company in a low tax jurisdiction. Check Stripe Atlas for Delaware companies registration for a start: https://stripe.com/atlas

First you will have local presence and more trust, second you will avoid risking a drastic decision affecting international sales, which we all see can happen really fast these days.