Thanks for reaching out.
I think it's a great idea to expand your audience and begin to ship to other countries! If you would like to sell your products to the US, you will need to add the US as a shipping location to a shipping profile. To do this, you will need to navigate to Settings > Shipping and Delivery to either add the US to the general shipping profile or create a new shipping profile. If you are only wanting to allow only specific products to be purchased from your US customers, you will need to create a new shipping profile with the products you are offering.
Once that is completed, you can then begin to set up the rates for that location.
This will allow your customers from the newly added location to complete the checkout process. Feel more than welcome to checkout our advanced shipping setup examples as it can help visualize how you would like the shipping rates to be setup.
Let me know if you have any questions, happy to help out.