The truck driver, plumber, electrician and all the other parallel businesses will not go under if Wal-Mart goes under. They will adapt and work with the business or businesses that replace Wal-Mart with a more efficient business model. That's how capitalism works.
When one business fails, another better adapted business takes it's place. It's survival of the fittest in economic form. When Wal-Mart fails, and the government bails it out, Wal-Mart is not forced to adapt to make itself more viable, and its competitors are screwed out of true competition.
What you described is socialism.