But entitlements are not sustainable at their current growth rate.
Per that picture, interest on the debt is really what is unsustainable. Entitlements grow relatively gradually and seem to be coverable with revenue restructuring. Something like 7.5% increase in absolute tax revenue or a 33% relative tax increase. Getting rid of the Bush tax cuts (for everyone) would be 10%. Removing the payroll tax cap would probably be another 5% of that. Corporate and loophole reform would probably get another 5%. Reforms to cut that rate of growth of entitlement spending (raising the retirement age, Health Care Act reform, Part D repeal, etc...) might fill in the rest.
By any means, I don't know too well, but it seems do-able if we face up to our underfunded liabilities, and, well, fund them. We'd still be paying significantly less than most of Europe even after that.
Interest on the debt meanwhile, threatens to doom us all and probably needs to be faced within the next twenty years before it does spiral out of control. How to fix the hole? That's when we start having to make the harder decisions.