hi OrangeBubblegum,
I have also thought about teaching in the US! To answer your questions, yes it is possible for someone with a PhD from the UK to get a teaching job. There are US universities hiring people of different academic qualifications (and also nationalities), so why should there not be UK PhD-holders teaching in the US?
I think it is a possible career option! What you can do now, is to start looking online for job opportunities/teaching job vacancies advertised for US universities. Look at the entry requirements to see if you qualify for their work permit stuff (green card etc.). Meanwhile, increase your teaching hours (at your present university) or publications, whatever it is that will enhance your CV. Usually they will ask for teaching experience etc. as well in your application.
besides looking here, also look at the websites of US universities for job vacancies! There's always something! It's up to you to find it!
good luck!!!
love satchi