I used to think that maybe all British people were selfish but actually I think it's just you.
At first I thought that maybe all British people were selfish but now I think it's just your personality
「最初はイギリス人はみんなわがままなのかもしれないと思っていたけど、ただ単に君がわがままだったんだね」= I used to think that maybe all British people were selfish but actually I think it's just you. / At first I thought that maybe all British people were selfish but now I think it's just your personality
※わがままじゃないイギリス人もいますよ(笑)
パターンとして考えると:
I used to think ~ but now I think ~
At first I thought ~ but now I think/realise ~