Japanese people aren't as fluent in English as people from other countries
Japanese people aren't as good at English as other foreigners
どちらでもいいです！
to be fluent = ペラペラ
people from other countries = foreigners = 外国人、他の国の人
to be good at = ***が上手
*as *** as* というのは
***は***ほど
という文法です。
比べるために使われています。
役に立てば嬉しいです！
I don't think Japanese people speak English as well as people in other countries.
この場合、次のような言い方ができますよ。
ーI don't think Japanese people speak English as well as people in other countries.
「日本人は他の国の人たちと同じくらい上手に英語を話せないと思う」＝「日本人は他の国の人ほど英語が上手でない」
ご参考まで！
ロシア連邦 
カナダ 
