飛美國德州回程想停東京, 應該用邊間airline?

Should be Northwest or United, as they provide the best connections. For AA, no good as it is very very expensive(because they personally dont fly to HK, they partner with CX instead).

Northwest is very very cheap(both meanings) but you get what you pay for, so so-so. For United, it costs not much less than AA but at least it is not so poor like Northwest(because Northwest is still under bankruptcy protection).

我建議你乘搭美國西北航空公司 (Northwest Airlines, NW) , 來回經東京以後飛美國洛杉磯國際機場, 再乘搭美國西北航空公司內陸機到美國德州, 早機去晚機返

Hope you have a nice trip !

American Airline goes to Japan and Texas. But I think you'll need to make connecting flights. Try Expedia .com . they're pretty good.
德州邊個城市? San Antonio? Dallas /fort Worth,Houston?比較大的城市American Airline 都有直航,otherwise, 要轉機.

Northwest (西北), 佢都要經東京才到hk. 你可extend 張機票.