True, very broad spectrum. Probably too broad to answer in one go.
If youre motivated, check out the ATM Mag website, or even better try and get you hands on the past 3 or 4 copies of the mag.
In general you will probably find that staffing is the number one problem in all ATSU's. Operationally on a global stage the implementation FANS is slowly but surely edging towards what is often coined a 'seamless' ATS delivery. Of course the prime enemy of FANS is each individual country's socio-economic status-quo and territorial claims (sovereignety).
Should point you in the right direction.