Hello from Amazon Selling Partner Support,
 
We understand that you are asking why your ASIN -- is enrolled only in Canada for the Ships in Product Packaging program.
 
After carefully reviewing our resource, we have confirmed that only ASINs that fulfill the program requirements and are sold in the US, Canada, France, Germany, Italy, Spain, or the UK are eligible. 

Therefore, your ASIN --- enrolled in CA marketplace is the only one eligible for the program.

You can search for eligible ASINs via the program portal in Seller Central.

To know more about the Frequently Asked Questions about the Ships in Product Packaging (SIPP), you may visit the link below:
https://sellercentral.amazon.com/sustainability/program/sipp