I drop off a package at the post office and the clerk who's right in front of me picks it up, and I point to the package and say to him this/that's an international package.
Which one is better there?
Probably "this" - you would most likely say to the clerk, "I want to send this to _____________; what is the fastest way?" or "what is the least expensive way?" rather than just pointing out the obvious (that the package is being sent internationally).