I'm a relatively new CM (still learning) so I will try my best to tell you what I know.
The US has this nation-wide healthcare program Medicare (public payor) for 65 YO & above, or those who meet the federal disability guidelines. Hospitals who want to receive payments from the federal government for taking care of Medicare beneficiaries must be accredited by the Center for Medicare & Medicaid services (CMS is federal). That means federal guidelines + state guidelines will be applied. There are several oversight entities that will survey & audit to make sure hospitals adhere to guidelines in their practice. Discharge planning & safe discharge is one of them. If there isn't safe discharge, patient is likely to readmit, which the federal government will stop paying hospitals in 2013 if the readmission (if it happens within a month) is related to poor medical management & lack of safe discharge plan. So the responsibility is shifted to the hospitals', and how they connect with the community network to prevent readmission, decrease avoidable utilization, & formulate safe discharge plan, etc.
As for commercial (private) payors, they mimics the federal plan; whenever Medicare changes, they kind of follow as well. I would say private insurance do pay for CM interventions, indirectly. For example, private insurance might want us to give concurrent reviews, reasons to justify why their member is in the hospital (are they hospitalized for medical necessary reasons, on a daily basis, and what is the plan). If a member has CM intervention needs but not intervened, that might lead to delayed LOS, and the delayed LOS days might be denied. But if the needs are intervened and pt. is transferred to next appropriate LOC, then their member's entire LOS in hospital is authorized and will be paid for. However, insurance do not dictate medical practice.
A day in the life of a CM will depend on the CM's work setting. It would be hospital, clinic/community, home health/hospice, insurance company, advisory/consultant company, worker's comp, etc. In a hospital, it depends on what model of CM the hospital chooses. Some CMs work heavily on discharge planning, some only work in utilization management, some in coordination of care, some do all, some do parts & pieces. I work in a hospital and do all spectrum of CM, so my day has a lot of prioritizing, prioritizing, prioritizing who to see first, who cannot afford to not being seen, interview pt. to learn needs & find out health self-mgmt behavior, social support, educate & advocate; and then looking at medical necessity, are patients in appropriate level of care, if not, what to do about it; insurance reviews; discharge planning...... i can go on for a long time.
I don't believe CMs in US have authority to prescribe, NPs do with MD supervision. However, we are the ones who contact insurance companies to obtain prior authorization for specialty drugs for pt. to continue to use in outpatient setting when discharged from hospital, we do have to have MD's prescription to do this.
Additional info: CMA*||* Discharge Planning