I can't grab a link right now, but the American Historical Association publishes a report once in a while evaluating the field. Their last was in 2013 and it showed that you do have slightly better odds with an Asian History focus, but if I remember correctly you still have less than a 50% of finding work in academia. Outside of academia, there aren't really any ways to track job success accurately. But in American non-academia there probably isn't great demand for an Asian historian.

So basically its a huge risk no matter what you choose and you can't really "plan" a history career anymore. It sort of depends on who you know and your timing, which no one can predict.

Try /r/AskAcademia

Here are some links of value, OP:

http://www.historians.org/publications-and-directories/perspectives-on-history/january-2014/the-2013-jobs-report-number-of-aha-ads-dip-new-experiment-offers-expanded-view

http://www.historians.org/jobs-and-professional-development/career-resources/data-on-the-history-profession