Hi esmesoma.
Just wanted to add some information to what karl*katz posted.
karl is correct in that using the Global Shipping Program is up to seller. One point of clarification though -- sellers CAN choose which listings he/she wants to list with the GSP.
Here is a quote from the FAQs page:
"No, you are not required to use the Global Shipping Program. If you enrolled through the interstitial, all of your eligible listings will automatically be enrolled. You can remove specific listings from GSP by unchecking the box or using bulk editing tools. If you enroll otherwise, you will be given the option to enroll all live eligible listings, or just future listings. You can remove it from your listings at any time."
Hope that helps.
---Ben