Hey Steve,
Yes, only available to customers in USA, Australia, UK, France, Germany, Spain and Italy atm (https://www.paypal-community.com/t5/Products-Services-Archives/Is-there-a-list-of-countries-where-PayPal-Pay-in-4-can-be-used/td-p/2977369). Most ‘Buy Now, Pay Later’ providers focus their service on certain countries to minimise their risk (eg. Paypal, Afterpay). So, you may need to use a service provider specifically catering to South American customers (maybe Kueski https://www.kueskipay.com/shopify) and integrate that with your site.
Since my post, I have actually removed the code from my Product Page for two reasons. One, it was creating some PageSpeedInsight failures, and performance loss, due to the connection it makes on page load to Paypal API. As a new site with an SEO and social focus to generate traffic, I wasn’t prepared to sacrifice the performance, and indirectly, the page ranking loss. Two, as you said, it was only adding limited info to the product page with no change to Checkout, and the customer has the option to choose ‘Pay in 4’ when they reach Paypal anyway. And I can just add a static image into the Product page template showing Paypal Pay in 4 is available. Code snippet for Checkout I don’t have, but if you are going to look at another service provider then the code will be specific to that provider anyway. Hope this helps.