The short answer is: everywhere. There is no place on earth that phlebotomists are not needed. Wherever human beings require the assistance of the medical profession, you will find phlebotomist jobs. And because no one, even in the most remote outposts, is immune from illness and injury, there is nowhere that a phlebotomist will be unable to find employment.
Phlebotomists can work in hospitals, laboratories, and doctor's offices. Phlebotomists can work at blood banks and at sites where donors give blood for transfusion. Phlebotomists can work at the scenes of emergencies or go from house to house to take blood samples from bedridden patients. Phlebotomists can work in any country at any time, even at such distant extremes as the Antarctic wastelands (where scientific expeditions have set up permanent outposts) or deep in the Amazon rain forests. Phlebotomists can work on ships or in mobile hospitals. Phlebotomists can accompany emergency crews on ambulances. In the future, phlebotomists may even work on the International Space Station. The sky isn't even the limit for the phlebotomy profession.
Of course, you may know precisely where you plan to work as a phlebotomist. Perhaps you have your heart set on working at the local hospital or at the local doctor's office. Perhaps you want to work for the Red Cross, which has a substantial need for blood-handling skills. If you already know where you plan to work, then you should contact someone there to find out what their requirements are for employment. Ask them what courses of study you need to take and whether you need certification before you can become employed. If certification is required, ask what agencies offer certification that the employer accepts.
As a phlebotomist, you won't lack for places to work. Phlebotomy is not only a profession with a future, but a profession that can take you to places you might otherwise never go. That's one of the things that make it not only a profession on which you can found a career, but an exciting profession that will change your life.