McDonald's is responsible for the actions of its individual locations because they operate under the company's standards. Every bad or good deed done by the individual locations are reflected back onto the company as a whole. As a result McDonald's has very strict rules on how it is run and how employees should interact with customers.
All companies, including McDonalds are responsible for the actions of their individual locations. Each location is a representation of the company as a whole and is equally responsible for upholding the good image of the company. Since the company itself sets the standards, it should be held responsible for upholding them.
While McDonalds is a huge company, their individual locations are franchises. Those individual business open their stores up with the company's expectations and procedures to represent the bigger trademark name. While money is a huge factor in being able to open up a franchise as an individual business opportunity, ultimately the trademark name and business image is the one responsible in the end. If any location has any issues, people will attempt to go after McDonalds. Since McDonalds is a franchise opportunity, they should ultimately be responsible for anything that a franchise location may go through.
When your name is attached to something you should always feel responsible. When something with food quality happens it not only affects just that location but also the whole chain. It makes a consumer second guess whether or not they want to eat there so if your name is on something you should always be worried about the location.