S.93 - I am not a visa expert, but it's my understanding there is a visa category that could allow you to become a flight instructor, then teach at the same school for a couple years to gain experience. Ask at potential schools.
I know more about the flying part...
The FAA will work with you to issue a private certificate based on your existing license. (
Airmen Certification ? Verify the Authenticity of a Foreign License, Rating, and Medical Certification)
Before you can fly solo, you will need a flight review. This can likely be combined with your training.
You can take a written test to add instrument privileges to this Part 61.75 certificate. This certificate can be used for further training that will be fully independent.
You will have to train for the regular instrument rating. Much of what you already know will help. If you do the instrument add-on under part 61.75, then any training you do in actual IFR can be PIC. This 'real' instrument rating is a requirement for the commercial certificate and includes both a written and a practical test.
Although the training can overlap somewhat for efficiency, once you have the IFR rating you can begin the commercial training in earnest. Again both a written and practical test are required. At this point, you can fly N-registered aircraft fully independently of your Pakistani (?) license.
Flight instructor training requires a written exam on Fundamentals of Instruction (FOI) and the CFI-Airplane written test. As mentioned above, the practical test for CFI can be pretty demanding. I've "heard" the FAA is a bit more willing than before to let an Examiner conduct an initial CFI test again. Ask how it works at the school(s) you contact.
If the examiner will let you fly the commercial test from the right seat, you can do the commercial training from that seat and have a huge head start on the CFI training. A really good instructor can help you develop a plan that takes what you have, minimizes wasted time/dollars, and fulfills the various FAR requirements as quickly as possible.
Good luck!