Which U.S. graduate schools offer the best MBA programs with a
concentration in Japan? I am looking for one that would give me the
best chance of landing a job with a top US and/or Japanese company
because of the reputation of the school and/or its job placement
prowess.

Are you looking for an international MBA program?
USC have a decent program, that only take a year to complete.

http://www.marshall.usc.edu/web/IBEARMBA.cfm?doc_id=1678

@rlasser --

How's your Japanese?  Without the language, it'll be pretty hard to
get a position at Japanese firms in Japan, but the foreign firms in
Japan will be easier to get into.  I've lived and worked in Japan for
close on five years, and have seen and heard a good bit, working both
at Japanese and foreign companies.

School-wise, two places with good international business programs and
excellent connection possibilities (networking while at the school)
are the Monterey Institute of International Studies
(http://www.miis.edu/) and Thunderbird (http://www.thunderbird.edu/). 
There are probably others out there too, these are just the two that I
know a little about.

Cheers,

        Eirikr

How about New York University's MBA program? Japanese companies look
for famous names. Also, many Japanese companies send their employees
there.  Expensive, but worth it.