I would say Miyazaki is probably the person closest to Matsumoto's generation in anime with much more of a beef with America. From his opposition to the American military presence in Japan to events like his Oscar ceremony snub ("The reason I wasn't here for the Academy Award was because I didn't want to visit a country that was bombing Iraq"), I would venture that if Miyazaki wasn't too big for anime conventions he still would be an unlikely guest for these reasons. His appearance at Comic Con a few years back was even remarked upon as unusual as such: http://herocomplex.latimes.com/animatio ... ott-of-us/ I'm not sure if Miyazaki ever surfaced over here during the era before his mainstream "discovery'.
Leiji Matsumoto visiting America would be an event on the order of a rare once in a millennia planetary alignment (La Metal?

** Actually, a mysterious new giant planet was recently inferred by scientists, confirming Leiji's vision in Queen Millennia. I'll thus take this as a sure portent of Matsumoto's impending American visit: https://www.caltech.edu/news/caltech-re ... anet-49523