Because of the Lucky Bancho Survey (https://luckybancho.ldblog.jp/wsurve...m?world=Global) we have good data regarding the number of characters per region.
JP: 326.817 which means roughly 10.213 per server
NA: 443.466 which means roughly 18.478 per server
EU: 181.024 which means roughly 15.085 per server

Going from the data NA should be even more effected but they aren't.
It also shows that currently JP has the best service since they have the least chatacters per servers.