Summary : It is not sustainable. Manage the Slow decline and blame right wingers.
If you set up your economy to incentivize bad behavior then productivity will fall, and no matter what else you do, the average standard of living must fall with it.
Starting at the top, government spending in general results in less efficient allocation of scarce resources as compared to private spending because the motivation behind government spending is not to maximize production or profits, but to attain power and control over people. So the larger percentage of your economy that is due to government spending the less efficient your economy will be, and the lower average standard of living will be the result.
Breaking it down to individual welfare, government spending creates the moral hazard of paying people to do nothing, or worse yet paying people to do the wrong things, like having children out of wedlock. This undermines the work ethic not to mention the fabric of the culture and ultimately the overall productivity of the average citizen falls.
Corporate welfare, and I include regulations tailored to favor one company over another in this, reduces the competitive forces that drive companies to win through creating the best product or service. If you are guaranteed a profit from the government, then why try hard? Again, productivity will suffer, and standards of living will fall.
In the long run we will continue our slide into second world status as our productivity falls to the levels of competing countries and our ability to maintain our military weakens as the money dries up. The goal of our representatives is to manage this decline in a way that keeps us from understanding that they've done this to us and eventually rebelling, while they stay in power by blaming people like Ted Cruz and the Tea Party for keeping them from implementing their next Utopian big government solution which certain to work THIS time... even though it was their last big government solution which creating the existing disaster, like ObamaCare.
Ultimately we become a welfare state where everyone is bought off in one form or another, and many people are dependent on the government for their very existence, while they live at a subsistence level and blame the villain-of-the-week for their plight.