It would definately be in salem massachusetts, think about it, Im pretty sure the whole country of England has been mapped out. This fact leads me to believe that there is some force keeping the muggles from seeing hogwarts, like the quidditch world cup, soo i don't believe the seclusion of the school plays the biggest part. I believe that if there were to be an American Hogwarts it would most likely be in some mountainous area near historic massachusetts, or salem. And another fact, who remembers the salem witch trials =D i feel like there should be some correlation between that event in history and the witches and wizards possibly creating an American wizarding school. The reason that i feel this way over the location stated by lovethewest in Colorado, Wyoming, Utah, or Idaho. Oh, is that people came to America (the colonies) almost over 250 before the American southwest was established. Im gonna assume that these wizards and witches didnt wait 250 years so that the American Southwest was established so they could create a wizarding school. However, i do believe they eventually could have founded one in that area because the American population is just massive, so there would probably need to be another school. Atmosphere is totally key in where the campus should be though, think of hogwarts, its rested beautifully in between the mountains. When i think of an american wizarding school campus in salem i think of a school rested on a rocky shoreline for some reason, which does go against my previous statement of where it should be near salem. I must say though, i unfortunately havent read all of the books yet
im on number 5 now, i started in may of 2011 and they are simply fantastic. what a beautiful mind JK Rowling has, full of creation, it inspires me to create myself, like my beliefs in an amercian wizarding school