Both Gaul and Britannia were conqured by the Romans from Celtic tribes that inhabited the region and both regions were invaded by Germanic tribes as the Roman empire declined (Franks, Saxons etc). Why did Britain developed a language that is considered (from my shallow understanding) Germanic and a culture that is often more associated with the Germanic culture while France, another territory occupied by the Romans but later taken over by the Germanic tribes develop a romance language (French) and a culture that is considered Latin?
Thanks for any info!
/u/cchiu23 's links to previous answers cover the main question pretty well,but I just wanted to add a note on nomenclature here. When they say a language is Germanic (or Romance, or Slavic and so on) they're talking about which language family the language stems from. It's not some form of quantitative statement about which languages it resembles most.
So English is a Germanic language since it originated from Middle English, which came from Old English, which came from Proto-Germanic. The fact that more than half of the English vocabulary is now from French and Latin doesn't change that. Another example is for instance that Norwegian is considered part of the West Norse branch of languages, even though, due to centuries of Danish rule, the Norwegian vocabulary (in the most-used dialects) now more closely resembles Danish, which is an East Norse language.
Across languages, basic words and counting words are the ones that are least likely to change, so that's where linguists look when they want to tell where a language came from. In that sense, it's still quite obvious that English is Germanic. "Hand, man, house" is "Hand, Mann, Haus" in German, "hand, man, hus" in the Scandiavian languages, and so on, and does not resemble so much French "main, homme, maison", which on the other hand does resemble "mano, uomo, magione" in Italian. Since both the Germanic languages and Romance languages are Indo-European, some words
As it were, there's a significant amount of words in French that are from early Germanic languages, even many common and basic words like 'boulanger' (baker) and 'regarder' (to look).
But in short, your parents are still your parents regardless of how much you end up resembling them.
Another historical episode worth considering to frame understanding of your question would be the Norman conquest of England. The Normans, despite having militarily conquered the English, did not make a decisive impact upon the language of the people they conquered, with French being the language of the court and nobility but not of the common people. The relatively small numbers of Normans who settled in England were eventually assimilated into the general population, and thus their linguistic impact was in the form of place names, varied vocabulary, grammar that has since disappeared from English, etc (I'm sure someone else here could speak better to this point than myself).
Roman Gaul, at the time of Frankish conquest, had been under the effects of Romanization for hundreds of years. Latin was prolific and the lingua franca of the territory by the time of Western Roman collapse in the 5th century. Germanic speaking Frankish invaders settled throughout Gaul, eventually intermarrying and assimilating into the general population. Their effect on the Gauls was like the Normans to the English, where they simply didn't have the numbers to actively displace the population and force them to learn their language like the Romans did to the Gauls.
Roman Britain was far more homogeneous than Roman Gaul was, with Celtic speaking Britons having remained the majority up until the Roman withdrawal. Where the Franks settled among the Gauls they conquered, the Angles, Saxons and Jutes actively displaced the native Celtic speakers and pushed them further and further west. The Celtic Britons under their dominion practiced intermarriage with the German tribes as well as lost their language to them.
In TLDR form: the Franks settled among and assimilated into a distinctly Latinized native population, and thus Gaul retained a Romance character. Meanwhile, the Germanic tribes invading Britain actively displaced the natives from the land they conquered (Look up the "Celtic Fringe" if you want to see this illustrated), and those native Celts that remained assimilated into and learned the language of their Germanic occupiers.