The boys were as nervous as the girls.
When I read the English translation with “as…as” I remembered the construct “così come”. Is it possible that without the “così come” the translation should be “the boys were nervous like girls” which has a completely different meaning. Am I very wrong?
Interesting, I have no idea to be honest. Intuitively I would say that if you removed the definite article, it could be the case indeed " I ragazzi erano nervosi come ragazze.", but I could be way off, since the article does function differently in Italian.
Or “I ragazzi erano nervosi come delle ragazze”?
I think the article is what makes the difference, as suggested.
If you omit the article, as you noticed, the meaning changes. With the article, it conveys the sense of the English sentence, without, it would be like saying “the boys were nervous like girls”.
An alternative way to say this, a bit more precise, would be “I ragazzi erano (tanto) nervosi quanto le ragazze”.