If you do go the US for your instructor rating, have a look at American Flyers and/or AllATPs.
As far as I know, there is no set minimum for the number of flight or ground instruction hours for an instructor sign-off in the US which can lead to some 'interesting' situations. But the above two schools are pretty good.
There is a lot of differences and regulations to study, a lot of good material is available on the FAA website for free (such as the Pilots Handbook of Aeronautical Knowledge, Airplane Flying Handbook, AIM, etc.) For the written exams, you can use the online test prep from Sheppard Air. Pretty good and they guarantee a pass. You can study it before going to the US and save some time.
While you are at it, get your ground instructor ratings too. You essentially pay for the written exam and get another (or three) extra certificate to show. I found it useful in getting a ground instructor job at an aviation college.
By the way, I heard about only locals being hired in Maldives as FO, so do your research. I think Ken Borek Air of Canada has some contracts in the Maldives but Im not sure.
Good luck!