American foreign policy would only be AP if you were studying it in the context of American domestic politics (i.e. how the electorate/legislature/president/etc. affect the formation of foreign policy). The questions you originally propose are IR questions (how American foreign policy affects/is affected by international politics and international actors.
HOWEVER, if you are ACTUALLY interested in American foreign policy vis-a-vis Asia, then that is CP. And yes, if you are going to apply to PhD programs as a comparativist then you need to have a regional area of interest (but not necessarily for IR).
Your best bet is to talk to your professors about these issues. The demarcation between these areas of political science were not clear to me until I actually sat down with my adviser and went through them and then did my own research (of course the lines aren't cut and dry and will always blur at the boundaries). I highly encourage you to hold off on grad school until you have a better grasp of the discipline.When you do apply, you should have one or two STRONGLY focused questions that you are interested in... not a whole bunch of half-baked interests.