Americans are desperate to "build" a potential US winner for US Open, even by picking the crappiest of all...
Oh please, I'm American, and I understand that Mardy's just having a good run (just a good tournament even?) and is not a consistent world beater. And I definitely don't think he'll win the Open. Your phrase would have been better revised as SOME American commentators and insane fanboys
As someone else mentioned, show me a Mardy who will blast aces and serve confidently two sets down in a Slam final versus the two greatest players of this generation. Then we can call it a top 5 serve. But, for now, it's very solid, very dependable. But I wouldn't make any big generalizations about it.