I am working with my client on building out two Shopify Stores (one for USA one for AU) which are on different stores.
I have built a landing page for this using PageFly which will sit on the US site:
When I set this as the new 'Home Page' I would still like to keep my current home page as an internal page '/usa/'
You can assign other page as home page.
And homepage can be assign to the internal page.
By customizing theme from admin.