This does not seem to be true currently. In 2025, there were 45356 McDonald's restaurants worldwide and 13706 in the United States, which is about 3.3092.

https://corporate.mcdonalds.com/content/dam/sites/corp/nfl/p...

However, in 2023, the numbers were 41822 / 13457 = 3.1078, which is (almost) within 1 % difference.

https://corporate.mcdonalds.com/content/dam/sites/corp/nfl/p...