Student Exchange Programs

Hi, I am a sophomore student in Japan.
I would like to go graduate school to work as a UN staff or a staff at organisations related to UN.
But I have no idea which college to go.

I am now studying Global Studies focusing on Non-governmental organisations, environmental problems, Human Rights, and things like these.
I would like to work at UN related organisations, but i have not decided which organisation to work.

And this year, I am going to a private liberal arts college in US as a exchange programme student for one year.
My GPA score is now 3.9 points.
My TOEFL score is 85. ( maybe my english skill will be improved during exchange programme…)
At my university in Tokyo, the half of courses I am taking are taught in English, and I can mostly understand.
I would like to get scholarship, too.

Please give me your advice!