Delta Green Friendly said:
Sam is a veteran of just about every war the US was in, officially or not, since Viet-Nam. For Sam Fisher to be in fact Harry Potter would require time travelling, and thus, Pime Taradox.
Second, Harry Potter is nowhere near competent or badass enough to be Sam Fisher.
Okay, so Harry got caught up in a time spell and sent into the past after being de-aged. He lives Fisher's life until 'Conviction' at which point he remembers everything that happened to him in both lives. Now since the Voldemort threat has passed by this time, 'Sam Potter' or 'Harry Fisher' splits his time between 'policing' the Wizards
and spending time with his daughter.
So, we can say that after the disappearance of Harry Potter from the wizarding world things went straight to heck. The Pure blood wizards have resurged, determined to rule mud bloods, squibs and muggles with an iron fist. However they aren't powerful or numerous enough to do this openly so they work in secret through various intermediaries and other organizations throughout the human and wizard worlds.
Sam Potter uses his talent for magic mixed with his veteran skills to oppose the pure bloods, and prepare the various governments, militaries and intelligence groups throughout the world to oppose this magical based threat.
....might need some work but.....