Is there any way to link up which designer works with which contract manufacturer (or at least the models)? And are there any exceptions? I seem to recall Alienware stuff was made in Florida at some point.
Search for schematics, or look for identifying clues on the motherboard. All the OEMs have more-or-less distinguishable styles and part numbering schemes. E.g. a part number beginning with "LA-" followed by a few digits, then possibly another character, indicates Compal (LA-8331P, LA-4921P, LA-A994P.) Inventec likes to use 6050Annnnnnn (6050A2266501, 6050A2493101.) Quanta uses a few characters/digits code (e.g. ZHY, LX89, ZE6.)
Alienware is just owned by Dell now and seems to put out overpriced poorly built chunky machines that target gamers with too much money. Razer and Falcon NW might be better from the chassis design side, or Sager and Clevo from the OEM value side.
The Alienware laptop I had for a week or two a few years ago was the worst laptop I've ever used. Noisy and hot and expensive and poor ergonomics and just all around unimpressive, poor hardware masked by a once respected brand name.