Common, you must be acting like...............to ask about scope of nursing in US? Possibly there is no way to transfer any of your Nepal credit to US college, as per my understanding but if you start here then you can transfer from one univ to other easily for some extent. There is no way you can go for graduate school in US from Nepali 3 yrs IN  certificate.
If you are already in US then continue your undergrad or start the process of NCLEX_RN to get job asap. If not then its not a bad idea to complete US undergrad in Nursing.
Good luck