willbav8r has got it about right, the visa is the big problem. Compared with the JAR FI rating the FAA certificate is a walk in the park, as is the licence. If you've done the JAR CPL Skill Test and FI you should be able to cream the FAA ATPL and CFII with your eyes shut.
Remuneration is generally a joke and a majority of the schools are cowboy outfits who are just dying to rip you off - something to do with being frustrated colonials, I guess.
On balance, go for it. But, let's be careful out there!!