I'd imagine eastern Europe already has a lot of competition with payment apps. They use an interesting protocol if they are actually using lightning payments to facilitate all their transfers (it'd make sense but light be a bit dangerous exchange rate wise).

To me, the names strike and stripe sound very similar and that might be a bit of a problem (or by design if they're wanting to advertise where the other would be seen).

Also apps in the US might look nicer because they're designed to only work on one operating system (iOS), most other countries don't have a majority use of Apple and prefer usability over aesthetics (also the dominance of Android means they also have access to back buttons a lot more).