I don't think foreign amex issuers and us amex issuers know of each other. In other words you can claim residence and therefore have different amex's in different countries and amex would not be the wiser. If you can justify the account opening requirements you are good to go and get bonuses from other amex jurisdictions with no repercussions on your US amex relationship... keep in mind most people are not able to do that so you won't get many experiences here on FT.

PM me and can share some tips.