Hi america

>If I moved to USA how long til I could own a firearm?

Once your a lawful resident you can buy a gun from a gun store. Though a court ruled that apparently illegals have 2nd amendment rights while in the US as well. But basically if you actually moved here because you got a green card or some other form of legal residency, you could walk off the plane and go buy an AK-47 in 15 minutes.