Hi ... I took the same route coming from Nepal to US (DC)....Bangkok -> Narita -> LA -> DC The airport at Japan and BKK were pretty convenient....unlike airports in the US. Especially at BKK, they have a lot of entertainment for transit passengers. If you need to stay at BKK airport for more than 12 hours, There is a transit tour train that you can show you around the city. I was in BKK for around 13 hours and i didnt feel bored at all. At Narita, the airport was crowded with thousands of passengers. At times, it was hard to find an empty seat. But the airport was pretty huge and had plenty of things to keep me amused. I dont know much about the way back though.....well...let me know if you wanna know more bout anythin else.....