Unfortunately, there is content in the libraries that will conflict if you load full libraries for different localizations at the same time. And, some parts are unique to each localization, so you cannot take a PLN that references one set of libraries and hope that it will appear correctly and without missing objects with another.
However, the PLA format (along with the embedded library) allows you to save a solo project with all library parts included with the file... so that the PLA will open for anyone. That's not really an option for Teamwork though.
Many (but not all by any means) international objects that are useful to users of a different localization can be found within the Object Settings (Window, Door etc Settings) dialog's Search function which will allow you to download that part with related macros/content and include it in either your local or embedded libraries.
Trying to extract just an object or two from a different localized library manually is frought with nerdy issues including macros, attributes and more.... and invariably will turn up with missing macros, wrong attributes etc. Hence BIMObjects/etc which offer some useful other objects that are standalone.
Lastly, in case I misunderstood your first question: yes, you can install as many different localized libaries as you like. But, a project will not be able to fully reference (include via Library Manager) more than one complete library without conflicts. So, you can work on a USA project, an INT project, a GER project... with all three of those libraries on your machine... but cannot combine all 3 libraries in one project.
One of the forum moderators AC 27 USA and earlier • macOS Ventura 13.6.2, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB
use North American for work in Imperial Units, and European for all Metric?
You could just create a dim style for each? In that way you do not have to get used to the intricacies of each regionalisation, unless you are actually working with local AC users in which case running the same version as them would smooth things out.