Coinpot adjusts its claim rates based on your location, and no the highest claim rate isn't just in the US. They work in the same way as this site, They have countries classified into several classes or tiers (ignore the multiplier in the pic since I don't know how exactly coinpot calculate their claim rates), so Countries in Tier 1 have the highest claim rates (You can check that yourself by using a VPN and you will see that they will show you equal claim rates ), Countries in tier 2 get lower claim rates and so on.

Again, ignore the multiplier, since this pic is from another site that follows the same concept, Hope that helps clear the confusion abit

https://i.imgur.com/aIIMm4P.png