cannot choose Amazon-partnered carrier

You can only use Amazon-partnered carriers if you are in the same country. Here is the excerpt from an article:

"Finally, you’ll need to select your shipping carrier. You can select either an Amazon-partnered carrier such as UPS, or a non-Amazon-partnered carrier.

Amazon’s partnered carriers are often much cheaper than non-partnered carriers and also come with the added benefit of payment being processed directly through your Amazon balance.

However, they are only currently available when shipping into Amazon from within the same country. Perfect for shipping product in from your 3PL warehouse.

When you ship to Amazon FBA direct from overseas, choose the non-Amazon-partnered carrier option. If you don’t know who the carrier will be, just select ‘Other’.

Finally, review the details and when you’re ready click ‘Accept charges and confirm shipping’ (it will say this even if the costs are zero) and you’re ready for the final step."