Assuming you're are really open-minded, I'll elaborate. I'm speaking from my experience as a physician (was a PCP
for several years and currently am a pulmonary/ICU doctor)
-The obesity epidemic has also affected Canada (although not as badly) - their healthcare costs are still much lower.
Obesity is a chronic disease w/ complications that are generally managed with outpatient care rather than inpatient visits (diabetes, hypertension, sleep apnea, etc). In a single payer system, all obese individuals would have primary care - well managed diabetics will avoid complications landing them in the hospital (foot infections, hyperglycemia etc) thus saving money. The same applies to other chronic diseases. Without a PCP, those with chronic disease are poorly managed and end up in the hospital without insurance for expensive inpatient care that they can't pay. The cost is passed on to hospitals and patients with insurance (including Medicare).
I am not claiming that access to a PCP will prevent hospitalizations for all patients but it will help for many.
-Drug/alcohol abuse - same principles as above. Outpatient care helpful but likely not as successful as for other chronic illnesses in terms of preventing hospitalizations.
-A single payer system would be much easier to deal with for providers (I am one). You are only dealing with one insurance plan. You don't have to hire administrators and staff specifically to deal with prior auth, billing from the myriad of insurance providers we currently have. Costs are lower and savings are passed on to patients. Doctor waste hours on this stuff that should be spent seeing patients. Also Medicaid is eliminated which doesn't make any money for providers anyway.
Overhead costs from CMS are high, I agree, but dealing with 14 different insurance plans makes overhead even higher. Many CMS regulations are really designed to lower Medicare payments anyway. Over time as healthcare spending decreases due to access to primary care, Medicare spending per capita will decrease and so will CMS regulations. Not to mention the 'intermediaries' for Obamacare are no longer needed...eg Centene.