Sorry, I'm not familiar with your implementation, but I would imagine having region as a selector for search results means there is some sort of regional faceting available. How is that accomplished?
ccTLDs are a useful signal, but not for US results. In this case, Sweetwater === https://www.sweetwater.com, and that has a US address in the footer on the first page.
To show accurate regional search results I would imagine these and other signals are being used within the index, and could be repurposed for these sorts of purchase links, too.
But it does become non-trivial when considering international shipping etc. Maybe it's not a (pragmatically) solveable problem to hide those links.
What about prioritising regional results, though? For example, here's another set of search results for me for this mic:
The amazon.com.au, storedj.com.au, and djcity.com.au links would be perfect as regional results over in the purchase links.