Why French language was able to survive as a monolingual spoken language in Canada despite Quebec being so close to The Thirteen colonies (Quebec shares border with New England), whereas California became completely English speaking despite being located so far away from the Thirteen colonies? The whole southwest was part of the Spanish empire and particularly in California virtually all the most important cities have Spanish names Los Angeles, Sacramento, San Francisco, San Diego ,etc. So I supposed that the Spanish presence was pretty significant.
The main reason for this is the California gold rush, which caused thousands of Anglo-Americans to move to California and establish themselves as the dominant cultural and linguistic group. The first California state constitution was actually written both in Spanish and English, with both language versions being equally official, but later revisions were only in English. Another factor is the size of the Romance-speaking population at the time of conquest by the British/Americans: Canada had something like 50,000 colonists, while there were only about 10,000 Californios. Montreal had 8,300 residents in 1760 and Los Angeles had only about 3,000 when it was captured in 1846. The 1852 California census counted 260,949 residents (ignoring most Indigenous people, probably totalling about 150,000). The Anglo-Americans pouring into California overland and by sea (after either sailing around Cape Horn or passing by land through Panama, Nicaragua, or Mexico) in search of gold numerically overwhelmed the Spanish-speaking Californios. There was no similar incentive for mass migration of English-speakers into Quebec, and as California was incorporated into an already majority-English-speaking country there were no constitutional protections entrenching the Spanish language at the national level and no national narrative of two founding peoples. Today California has a very large Spanish-speaking minority, about 1/3, but this is mostly due to more recent immigration from Mexico and the rest of Latin America rather than descendants of the pre-gold rush settlers, and Spanish remains a minority language. As part of the English-only movement and a general backlash against Mexican and Latin American immigration, a ballot proposition in the 1980s made English the sole official language of the state (although many official documents are translated into the largest minority languages including Spanish, Tagalog, and Chinese, and court interpreters are required by law when cases involve people who do not speak English proficiently).
Quebec's unique situation stems from the aftermath of the Seven Years War (French and Indian War in N. America) and the British conquest of New France. I recently answered a similar question here about how Quebec managed to protect its language and culture despite British rule and an overwhelmingly anglophone presence in America. u/enygma9753
You will find more context in the link above on the 1774 Quebec Act, which enshrined French language rights (as well as French civil law, religious and property rights) under British law and helped to diffuse political tensions in Quebec -- while enraging sectarian English Protestants in America -- just before the American Revolution. The British also found common cause in Quebec with both the Catholic Church hierarchy and the landowning seigneurial class, who promoted loyalty to the Crown and portrayed revolution and republicanism as the path to anarchy.
These linguistic and cultural protections would be reaffirmed in 1867 when Canada became a self-governing dominion. Quebec would remain wary of English Canada's commitment to protecting French Canada's linguistic and cultural identity throughout the 19th and 20th century.
Successive federalist and separatist Quebec provincial governments would agitate for and win special powers from the national government to protect its linguistic and cultural heritage. When this process stalled or became divisive, Quebec elected separatist governments in the past, who have argued for EU-style sovereignty association or even independence from Canada. You can also read more about this complex issue in the above link.
In contrast, U.S. federal and state laws advocated for the anglicization of regions under its control and promoted assimilation of linguistic minorities into an decidedly anglophone American identity. This process would continue into the 20th century.
An interesting footnote is that France ceded Louisiana to Spain in 1762 in a secret treaty, just as the Seven Years War was concluding. Spain was an absentee landlord there and didn't really develop its claim beyond New Orleans. France would only reacquire Louisiana under Napoleon, who then quickly sold it to the U.S. for $15M to finance his military campaigns in Europe.