Silent,
Unless you have the right to work, (work VISA - there is a specific list of jobs that you can be granted a work VISA for, or a Green Card) you will find it almost impossible to find work as a flight instructor here. There are a few schools that let you get un-paid (i think) "work experience" as a CFI through a special student VISA permitting loop hole which they were grandfathered in. My memory on this isn't 100% clear so there may be aspects that I'm getting wrong. However, in general, it is very difficult to work as a CFI in the U.S. unless you already have the right to work here.