Well not a vocal supporter but I am pragmatic enough to see that single-payer in the US is most likely inevitable. The federal government currently manages through funding and administration nearly 67% of national healthcare right now, today. So it is only a small step to 99% or 100%. 
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"Tax-funded expenditures accounted for 64.3 percent of U.S. health spending – about $1.9 trillion – in 2013... The Affordable Care Act will push that figure even higher by 2024, when government’s share of U.S. health spending is expected to rise to 67.3 percent." http://www.pnhp.org/news/2016/january/government-funds-nearly-two-thirds-of-us-health-care-costs-american-journal-of-pub
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Of course the organization that manages two-thirds should accept responsibility for an equivalent percent of the blame for the higher healthcare costs and poorer medical outcomes in America.