Hope that you folks can help. The title and the author completely elude me but it's about how Lord Voldemort became a ghost after the events of Halloween 1981 and stalked Harry eventually regaining his body due to the blood wards on the Dursley's house. He then sets up a whole persona as Harry's twin (which included going to America) and eventually manipulates his way to the top of the wizarding world. It's a great story and I hope you can help me find it.
Welcome to Stack exchange. I know of a couple of similar fanfictions, but I think the one that describes it best is "Yes, I am Harry's brother" by Ynyr. It fits your mould perfectly, including Voldemort (calling himself Vito) going to America and him sitting as the Supreme Mugwump of the ICW as well as the Head of DMLE.