@R_Escobar
The most marketable things for university teaching are publication track record, excellent dissertation (and ability to communicate what it is in the job letter/talk), and teaching experience. If you're in an interdisciplinary field, then you'll still need to publish in history if you want a job in a history dep. that requires scholarship. So my argument is that one isn't better than another, it's what you do with it while you're a student. You might have more explaining in an interdisciplinary field (but maybe not, b/c you'd have to argue for fitness in an interdisciplinary dep. if you're just history), but it really comes down to good scholarship and good teaching experience and fitness for the job opening. I think there's more "wiggle" room in interdisciplinary studies like Am. Studies, but that's only going to be "marketable" if you're savvy about it.