Power supply safety standards
Honestly, it's not that big a deal.  The simple way is to do an end-run around all these issues:  Use a low-voltage wall-wart power supply which is UL/CSA/CE listed.  The rest of your project falls under the low-voltage rules, which are  more relaxed. 

If you absolutely need 120V inside the box (why?), make it an all-metal box and ground it, use listed devices for anything that portrudes, and be safe inside. How else can anything get prototyped? 

By the way, for access to the standards, there is a bit of a rebel movement going on.  It rejects the notion of creating a de-facto secret law by referencing a private entity's standard and subcontracting the private entity to selectively paywall, signupwall, creditcardwall, agewall, classwall, enemy-of-the-state-wall, etc. The standards organizations are answering this by providing some degree of freer access. So you may be able to get access one way or another.