They would find another way to advertise if it wasn't through the PL. The reason these companies can spend so much on adverts is because we as consumers desire their products so much and are willing to pay the demanded price for them. Do you really think that hamburgers and coke cost as much as...
There are multiple millions of US$ that are being paid by these US companies to the Premier League that without that money the league would be nowhere near the quality that it is today.