There is ample work for freelance FAA instructors around the world, but some countries make it hard.
For example in the UK you cannot do any remunerated training unless you also have a JAA FI Rating, and if doing remunerated training in a foreign reg plane the plane's owner needs DfT permission... one way is to fly outside UK airspace for the training portion of the flight.
Also the political climate in UK GA can make it hard to do it at certain airfields. The based school will complain to the airfield and the CAA, and try to push you out of the way. Freelance instruction needs to be done discreetly, and some UK based FAA instructors prefer to fly out to France for any stuff which needs a runway for "obvious" training e.g. glide approaches.
I never knew that JAA FIs are taught how to teach. Half those I had for the JAA PPL couldn't teach at all.