PCT Countries and Regions

The PCT Contracting States and their 2 Letter codes can be found here:
https://www.wipo.int/export/sites/www/pct/en/list_states.pdf

Now in many countries you can either enter that country directly or via a region that that country is a part of. If you enter directly then that country handles the examination and issuance. If you enter a region then the patent application is examined by the regional authority and if allowed you must then enter the countries you want in that region via what is called a national validation. National validation does not require another examination and basically consists of putting it into a proper language and paying some national fees.

So let’s look at some countries on the list_states.pdf you downloaded from the above link.
Look at US United States of America and you see its 2 letter code and nothing further. Same for AU Australia. These countries you can enter only directly.

Now after some of the countries you will see in parentheses a notation which at the bottom of the page explains the region it is part of.

For example, NO Norway (EP) has the (EP) notation which indicates that Norway is part of European patent region (the EPO – European Patent Organization). It can also be entered directly.

Now for France FR you see (EP)2 which indicates France is part of the EP and you CANNOT enter France directly – that is you must file through the EP.