$18 shipping for a $20 FBM order??

I have an Amazon seller FBM order that has to be shipped to some armed forces in Europe. At least that what it says when I look up what abbreviations APO, AE with a 09263 zip code.

I’m in the USA. Why is Amazon letting customers outside the US buy my items and then make me pay insane shipping rates?

I’m not enrolled in any other marketplace besides the U.S. is there a way to prevent this from happening? Or maybe set location based shipping which the buyer pays for?