Well, I’ve never thought of the structure of French and English being similar. Despite knowing French better than any of the other languages we’re discussing (I know a little German and have a smattering of Spanish, Portuguese and Italian) I still have a hard time ‘thinking’ in French, whereas I find thinking in German pretty easy once you get used to the rhythm of it. I always attributed that to our languages’ shared roots.
Also, I’m pretty sure that adding vocabulary to a language, doesn’t alter the structure of the language or put it in another language family. Japanese has a lot of Chinese words in it - a lot - to supplement the native Japanese words but it’s still distinctively Japanese and not at all Chinese at the structural level of how the language works. There’s no way that knowing Japanese would help a Japanese person construct an intelligible sentence in Chinese, despite that borrowed Chinese vocabulary. I would say that’s the relationship of French to English: the French donated a bunch of vocabulary to our language during the time of the Norman invasion, but those words didn’t supplant the native Anglo-Saxon words, so that when we want to sound poetic or flowery we reach for one of the French-derived words, but for the most part we could get along without them. The vocabulary didn’t alter the structure or grammar of the language enough to create a hybrid of French and English (a pidgin). Most English people continued to speak English after the invasion even if it expanded their or their descendent’s vocabulary. Then the vocabulary expanded again during the Enlightenment when the explosion of scientific knowledge required a lot of new vocabulary, which was created from Latin and Greek roots.
Why would you say French is less of a Romance language than Spanish? What would make one ‘less’ Romance (as I thought it was just a matter of common descent)?
To me, Spanish and French seem very close, in fact I credit knowing French with the degree to which I can ‘get by’ in Spanish despite not having any formal training in it; whereas English and German seem very close - that’s why I picked up German pretty quickly and enthusiastically in school. I think if I had time to devote to it I could get fluent in German much faster than it would take me for French - or perhaps I should say took me since I did achieve semi-fluency in French. (Maybe some of that is misplaced but it helps if you like a language, and I’ve always liked German because to my ears it sounds like an archaic kind of English.) I’m also surprised to hear you say the idioms are the same in French and English, as I think I know a fair number of them in French but I thought they were completely different from our idioms. In fact that’s the definition of an idiomatic expression, I thought.