I can see the decline in Europe being unsettling, but I'm not really surprised about US/Canada. ~185 million is about 52% of the population of US/Canada [3]. If we assume 35% of the population is simply too young to use it (20% under 14 [2]) or too old to be drawn to it (15% is over 65 [1]), that leaves only 13% of US/Canada's population which are feasible MAUs no being MAU, which is crazy.

[1]: https://www.census.gov/newsroom/facts-for-features/2017/cb17...

[2]: https://data.worldbank.org/indicator/SP.POP.0014.TO.ZS

[3]: https://www.wolframalpha.com/input/?i=185+million+people+%2F...