ご質問ありがとうございます。
「いい感じに分かれている」はIt's divided wellとかThere's a good diversityとかThere's a good mixtureなどに訳せます。Hitomi様の説明文により、There's a good diversityとThere's a good mixtureがぴったりだと思います。
例文:Japanese people aren't focused on one particular sport. Instead, there's a good mixture in the number of people doing different sports.
Japanese people aren't focused on one particular sport. Instead, the number of people doing different sports is evenly divided.
ご参考いただければ幸いです。