Skims over rights for non US citizens. Does the US Constitution protect me at all in any regard, being a foreigner? The things the CBP can do with citizens is crazy enough, but from my understanding the things they can do with non-citizens is even more ridiculous.
The constitution protects everyone in the United states. The area before you walk in before going through customs doesn't count, although you do have some limited statutory protections. American citizens are protected because we must eventually be allowed into American territory at which point american law kicks in, but we are not guaranteed that our property can also come through the border.
My advice is always the same -- don't pass through any international border with anything you'll be too sad about losing. Countries are weird
