Security inconsistencies

A peeve of mine, and probably many other frequent travellers, is how the security arrangements are supposed to be there for our safety and yet there is a wide range of treatment and rules. This is particularly annoying for international travellers who have to cope with sometimes marked differences by country. Surely the same belt or shoe or laptop or whatever, doesn't suddenly become more dangerous just because I am in USA instead of say Australia?

For example a selection of security arrangements on my recent travels.

New Zealand - jet flight not to USA
No need to take anything off to go through the walk through metal detector (WTMD), no need to take anything out of bag to go through xray machine (XM).

New Zealand - prop flight
No need to pass through security at all.

Australia, Singapore, Spain, Argentina - not to USA
No need to take anything off to go through the WTMD although I put my wallet in my bag as a precaution, no need to take anything out of bag to go through XM.

United Kingdom
Take off belt and shoes for the WTMD and put watch and wallet in my bag, no need to take anything out of bag to go through XM, no liquids allowed.

USA
Take off belt and shoes for the WTMD and put watch and wallet in my bag, take small liquids out of bag and put in clear ziplock bag to go through XM, in several places debate over whether the zip on my bag qualifies as ziplock (geez), said bag plus small liquids confiscated at Boston (BOS).

Oman
Take off belt for the WTMD and put watch and wallet in my bag but shoes stay on, no need to take anything out of bag to go through XM.

Chile - not to USA
No need to take anything off to go through the walk through metal detector (WTMD), no need to take anything out of bag to go through xray machine (XM).

Chile - to USA
No need to take anything off to go through the walk through metal detector (WTMD), no need to take anything out of bag to go through xray machine (XM). Extremely cursory manual check of bag (largely consisted of opening up).


The only thing that is consistent is the inconsistency.