Having also been a foreign licensed Glider pilot(Canada), when coming
to the US its best to simply take the US training from scratch, if you
want a lifetime Glider Pilot lic.

In your case all your book logged flight time is credited towards your
US lic.

Just bring your log book, and you will need to be issued a US student
glider pilot permit, takes about 15 minutes at your local FSDO.

http://www.faa.gov/pilots/testing/index.cfm?print=go

Also start studying for your written test now(ASA Private Pilot Test
Prep), and take the online practice tests until you start getting 90%,
then you will be ready to take the actual written test at a testing
center. The pratice tests are identical to the actual.....although a
different subset of 30 out of a possible 500+ questions.

http://www.webexams.com/exam/view/153

Chances are high that you will get at least 5 of the 30 questions
exactly from the practice tests and are gifts from the FAA for those
doing the practice tests online.



Ray