As a medical related discipline, there is demand everywhere medical services are provided in approximate proportion to the population, however the main problem your wife faces is that the licenses to practice are issued at a state level, and her British qualifications are likely worthless. At best she may be able to take some additional training and take some sort of conversion exams, at worst she might have to take a whole degree program to be able to get a license to practice.
It is about impossible to say what the situation will be in 7-10 years, and her guess would probably be as good as anyone else's!
If you are in the UK, your wife's best chance at employment would be through an agency. Many foreign therapists practice throughout the USA with sponsorships through various US agencies. Also, for someone entering into PT education, a PHD is the entry level degree throughout the USA, unless they are seeking training at the assistant level (PTA) which is a AAS degree. However, a PT that has a BS &/or a MS is absolutely employable. PT is considered a pretty secure career, albeit mostly dependent on reimbursement for services (insurance companies) and it's also facing encroachment by other disciplines. To the best of my knowledge PTs have two disciplines encroaching; Athletic Trainers and Massage Therapists. Like OPs have pointed out though, employability will vary from state to state, and sponsorship will depend on supply & demand in any given state/city. Try these websites for further info: APTA (American Physical Therapy Association), Advance for PT (a professional magazine for PTs with job opportunities/foreign therapist info). Good luck!
Each state have practice acts which define the qualifications needed to obtain a license to practice in that state. It is my understanding that foreign educated health care providers are evaluated on a case by case basis to determine what if any additional classes, supervised practice or exam may be needed prior to obtaining a license to practice. The requirement for a doctoral degree is relatively new, and is the Doctor of Physical Therapy or DPT, a professional doctorate, and very different from the research/academic PhD. This web site may help http://www.apta.org/Licensure/StatePracticeActs/
so no state will allow her to have a licence with just a masters? no matter what?
Like I said, each state has their own requirements.
You'd need to look each state up.
I told you about one, Maine. I'm pretty sure MA is the same, but I'm not 100%. I'm sure you could google the states that you are interested in living in to find out what they require just as easily as any of could.
When I was born I was so surprised I didn't talk for a year and a half. ~ Gracie Allen
You can only be young once. But you can always be immature. ~ Dave Barry
Immigrants should be tarred and feathered....Yes, I like it kinky.
My understanding is that all entry level physical therapy degree programs are moving from masters to doctorate over a period of years, so eventually it will be statewide. There was a grace period for occupational therapists applying for a license when they did the same transition between BSc and MSc (which unfortunately I didn't know about as we moved here on 8 weeks notice). So there is nothing to stop your wife applying for a license before you move, and before the requirement changes, on the basis of her MSc. I would have done this in 2011 had I known we were coming in 2012.
For OT, there was a $1000 application fee for them to assess the foreign qualification (in many cases UK degrees, particularly bachelors, are not viewed as equivalent to US) and then there was an exam. I applied anyway, without a masters, and tried (unsuccessfully) to argue that 9.5 years of clinical experience was equivalent to an MSc.
The national body for OT was NBCOT, and they have a great website with lots of information for internationally educated therapists. APTA I think is the PT version.