Yamaha already has the V-Star 250 and the XT250 for beginners. I seriously doubt they consider beginners important enough to risk bringing something else in. Even though it is an existing model, it would cost a fortune to get it certified to sell in the U.S. Used to you could just bring a few over, if they sold well, bring over some more, if not, no big deal. But with DOT and EPA, it don't work that way no more.
2002 Vulcan 750 (engine out, slowly being disassembled) 2013 Royal Enfield B5
2001 XT225, 2009 Genuine Stella
2012 Zuma 125, 1980 Puch moped