The idea that tipping is mandatory in the USA is very ridiculous for most people. The idea that the person who spoke a few sentences with you and walked a few meters to bring your food should just get an extra 20% of your meal price is crazy.
If a restaurant isn't paying their workers properly, don't work there and the problem will solve itself. The only thing keeping that broken system afloat is the fact that many waiters and waitresses don't have the financial flexibility or capability to quit or get another job.