How do I do customer interviews for a venture in another country while staying in the U.S.?

The short answer is, this is very difficult to do remotely.  It is hard enough to primary market research in the same city when you need to resort to using video chat or a phone call because you cannot find time to meet with interview subjects face to face.  You also lose situational awareness when you cannot run your interviews in context - in the place where your end users live and work and use the product.  These problems are compounded a hundredfold when the interview subjects reside in another country with completely different cultural norms, technical infrastructure, and everything else that makes every basic assumptions highly questionable.  It is almost impossible to get a true sense of the target end users unless you are on the ground, immersing yourself in their daily life and watching how they work and play.  You really need to find a way to get out there to the target country and do the field work on site.

That said, trips to another country for primary market research are costly from a cash and time standpoint, so it behooves you to do some early research to try to get a basic sense of what you might be dealing with when you do get out there, so you can hit the ground running and not lose any valuable time while you are on the ground.  One way is to build relationships with people who do live there so they can help make connections and find interview subjects for you to talk to on the phone or via Skype.  While not perfect this indirect interview vehicle will still give you better data than just secondary research.  You can formulate hypotheses on buyer and user personas and the full cycle use case so you can concentrate on testing these hypotheses while on the ground, rather than formulating new hypotheses and then recruiting subjects to test them with.