He talked to everyone as though the mistake he made was my mistake.
He sounded as if it were my mistake and not his when he talked to everyone.
この場合、次のような言い方ができますよ。
ーHe talked to everyone as though the mistake he made was my mistake.
「彼は彼のミスを私のミスかのようにみんなに話した」
ーHe sounded as if it were my mistake and not his when he talked to everyone.
「彼はみんなに話した時、まるでそれは私のミスで彼のミスではないように話した」
ご参考まで！
He made it seem like his mistake was entirely my fault.
ご質問ありがとうございます。
・「He made it seem like his mistake was entirely my fault.」
（意味) 彼は自分のミスをあたかも私のミスのようにみんなに話した
<例文>He made it seem like his mistake was entirely my fault. It wasn't fair.
<訳>彼は自分のミスをあたかも私のミスのようにみんなに話した。不公平だったよ。
参考になれば幸いです。
カナダ 
アメリカ合衆国 
