Amazon Prime Video application should be available in all countries where the service is available, in particular in Poland
I see no legal or technical resons for making the application available only in US and UK, as the service is available in Poland for some time already.
BTW, I've been mislead by the mail from Oculus (Big announcements. Huge additions.) which didn't mentioned the limited availability of the application and created the Prime account unnecessarily (fortunately they have a free trial period).