You need to call your finance and ask her if she would like to have a wedding in the States and listen to her reaction to that answer. If the reaction is positive, then just ask her directly. If the response is negative, find a way to make her be the one to want to have the wedding in the States. Try and use some reverse psychology and see if it helps.
You should not tell her how much you want her to do it. Tell her from the perspective of, how much better it will be than the place she is living now. The benefits, and facilities, and the work opportunities she would not enjoy anywhere else.