To the original post, Johns Hopkins is a great place, particularly SAIS. One thing you should keep in mind is that JHU's main campus is in Baltimore, but the SAIS campus is in Washington, DC. Given that in Baltimore, gangs have made DVDs of their crimes and handed them out around the community, this is a definitely a bonus.
But the biggest differences between the various U.S. IR programs hasn't really been mentioned yet. Really, you have a number of top contenders:
1. SAIS (Johns Hopkins)
2. SIPA (Columbia)
3. Fletcher (Tufts)
4. SFS (Georgetown)
And a couple "second tiers" (still good, but not quite the same weight):
1. Elliot (George Washington)
2. Yale
3. University of Chicago
4. Monterrey, etc.
Notice, also that public policy programs like the Kennedy School (Harvard) aren't up here either. They are generally different beasts altogether.
Of the top four, they vary widely in their focus:
SAIS - heavily economics-oriented, lots of people come out working for the World Bank.
SIPA - partly because it's in New York, it's less tapped into U.S.-based politics and quite naturally focused on the UN and other international institutions.
Fletcher - The legal aspect of their degree is optional, but most people I know who went there do have some form of international law concentration.
SFS - more or less equals State Department.
And by the way, the rankings for U.S. IR programs are crap. There are few enough that it's difficult to apply metrics, and those are largely meaningless anyway. Also, you should know that international students have a much easier time getting into these programs than do American ones. In addition, people in these programs tend to be older than those who do similar programs in the UK. There's a far higher premium on work experience in your application.
Good luck!