Earning a PhD even inside the US is no guarantee of a tenure-track job these days.  It's a very competitive market: more folks are getting doctorates, and more academic departments  are cutting back full-time hires in favor of part-time positions.

Keep this in mind as you make your decision.  Getting a PhD has many wonderful aspects to it, but guaranteed employment is not one of them.

What citizen said.

I did phd at u of Tokyo which is ivy school for Asia. The Metabolist movement started there and it remains a powerful career starting point for its graduates. But I still had to work for a few years as adjunct professor for low pay before getting a proper position. And even my current job is non-tenure 5 year project. I'm cool with that since I also run an office but it is not ideal. My position is entirely typical and only a few friends have gone onto tenure positions. They are not that common anymore as universities replace them with term positions and adjunct profs. If you want tenure nowadays seems like you might need to at least write a book or two and or do something that makes you famous in professional world.

Not quite related but if you want to teach at the better schools it helps to do phd at the highest ranked Uni you can. Most of my colleagues did their PhDs at same Uni as me. It's ranked no 1 in the country so the administration likes to have us there in order to bring up their own profile (or so I presume ). It seems to be a rule that they hire from above and almost never from their own graduates, nor even sideways from their rivals. It is an annoying but clear reality and probably a big reason I have a job. My current uni is also quite well known, with two pritzker winners in faculty. But if I'd done phd elsewhere I would be SOL.

Academia is a surreal world.

Yup, most open positiions seem to be for adjunct profs. Getting a tenure-track job means you've got something special going on.

What would a PhD in Interior Design even entail? Usually PhDs are very research intensive and you have a major prof that guides you through the process of conducting legitimate research. Would think having an excellent major prof with connections back to the US and an outstanding body of research / books/ publications would be what you want to look for.

Sorry Will, not to derail this thread, but what about Tokodai? Most of their professors seem to be from Tokodai, and lots of famous architects have come from there. Would that be an exception in Japan?

No it can happen and not all schools are the same, depending on politics of the faculty.
Keio and waseda seem to take a lot of their talent from todai. Todai itself seems to invite its graduates back to teach. The national schools seem to do a lot of that. But once outside that bubble seems to be the rule that schools like to have profs from the most respected schools possible.

I'm definitely cynical but all things being equal it is easier to teach at u of wherever if you go to Harvard than the other way round.

Funny enough that was pointed out to me when I was applying to phd programs. The prof I first thought about working with gave me career advice of going to better known school and made introductions so I could do so. Really changed the course of my life, without any question. I would never have gotten the teaching gigs I did if he hadn't pushed me that way. It's only years later that I can see what he was talking about actually so am quite glad for that frank advice. Academia is nothing like I imagined it was as a student.

Ciao Maria:

I've never seen any of my instructors' CVs or handbook info displaying PhDs from foreign schools other than a few German and Swiss ones, it seems.  I would not want to be educated in architecture or a design field in Italy, especially if you want to come back to the States.  They are veritable factories and, at the undergraduate level, I've heard of otherwise talented students who encounter a snag with a prof. and their design sequence is unnecessarily altered or delayed.  Since there are no private architecture schools in Italy, is the Politecnico di Milano the country's best design school?  Not Firenze or  Roma-La Sapienza? I don't know, but if you were schooled in North America, I would continue your PhD work here and try for the best ranked school.