Once you get a license in the US in your initial state, and that means having a an actual license number assigned to you, you are free to endorse that license to another state. But not until you have the actual license number. When you take the NCLEX for CA, Florida, or other states that will not grant an actual license until you have a SSN#, you do not have a license to practice as an RN in the US, so therefore cannot endorse. They only give you a piece of paper that states that you have passed NCLEX exam, but it is not a license. They can verify that you have passed NCLEX for the Visa Screen Certificate, but they cannot verify a license, and that is what is required for endorsement.
Once you take the NCLEX exam, the exam has reciprocity. Meaning that you do not need to take it for another state, your score is accepted by all states.
To endorse, the exam score can be used, but that is only one part of the licensing process. Some states have language requirements, others have extra classes that need to be done, like Florida and NY. Each state can also set their own curriculum requirements, and it may be more stringent than what is required for the VSC. It is up to the individual state.
