Red Dragon,
You can go and work in the USA if you want to. Like almost all other countries if you have a skill that can not be found within its own population or if an employer has tried to recruit someone but has had no success, they can then hire a foreigner and apply for a work visa.
If you train to be a nurse I expect you will be able to find a job in the US. If there are enough controllers in the US why should they hire foreign ones? There are not enough in Aus so they hire foreign ones. Simple really or are they sour grapes?