Yes, because Amazon is country specific like Amazon India, Amazon China etc.
You can only sign up for any specific country you want if you are focusing on selected countries only.
If you want to target every country then you can use Amazon Onelink.
Other than India and China, all countries are available in onelink.
Onelink will redirect the visitor to visitor country Amazon site as long as the same product is available else it will redirect to related products page.
Don’t use any third party plugin as they are unreliable and take a commission also.