Is English in the US Threatened
by Other Languages?
Almost all anthropologists say no.
Historically, the languages of immigrants follow a three generation rule:
First generation: migrated as adults or older adolescents, usually learns some of the language of the new country, but does not speak it like a native.
Second generation: born in the new country: Generally bilingual (but often speak only the new language, even to parents).
Third generation: up to 90% monolingual English.
There are exceptions such as mid-Western German communities, and border communities. However, it's far harder to preserve an immigrant language than to lose it.
Next: What is culture?
In many ways language loss is tragic. So many of us wish that we were fluent speakers of the languages of our grandparents and great-grandparents. A dimension that kind of makes this a tragedy in a dramatic sense is that in so many cases, not being able to speak the language of a parent appears like a conscious decision we made as little children when we were far to young to understand that not putting in the effort to speak to parents in their native language would rob us of something we'd later long for. But, of course, it's much more complicated than that. First, national governments have a vested interest in linguistic uniformity and promote it, sometimes with great brutality. For example, China has repeatedly committed itself to at least 85% of its population speaking Standard Mandarin (the language of the Beijing region... there are almost 100 different dialects of Mandarin, many of them mutually unintelligible...so actually different languages). Famously, between 1879 and 1990 the US implemented a system of boarding schools for Native Americans, one aspect of which was that students were forbidden from speaking their parents' languages and harshly punished if caught not speaking English. The famously sticky Académie Française tries to impose the linguistic standards of Île-de-France, the region around Paris, on the French speaking world, and so on. HOWEVER, language loss is also a voluntary (sometimes conscious, sometimes unconscious) process.
Speaking primarily your native language is great if your life is contained entirely in the world where most people speak that language. If you want to be part of the broader world, not so much. It's almost certainly true that the majority of people, particularly young people, want to engage in the society they are part of. They want to be successful, however that is determined by their society. Further, parents also want their kids to be successful... and in many cases, they need their kids to be able to help them by speaking to members of the outside culture for them. Urbanization adds further pressure. In 1960, two thirds of the world's population lived in rural areas. By 2023, a minimum of 58% of the global population lived in urban areas, and some estimates pushed that number as high as 80% (it depends on your definition of urban). It's hard to retain your native language if you neighbors all speak a different language. If you only speak your native language, your job opportunities are also highly limited. If people are pushed into speaking only the national language by governments, they are equally pulled into speaking only the national language by the advantages it offers. Together these push and pull forces are juggernauts that have led and will continue to lead to language loss worldwide.
It's very difficult to know when a language is endangered. There are between 450 and 500 languages with at least 1 million speakers. Another 200 or so have at least 500,000. It's hard to imagine that any of these are likely to disappear any time soon. However, below that, it's anyone's guess. Whether a language is in danger of disappearance depends on numerous factors. The total number of people speaking it is one, but the question that is probably more important is do the children speak it to each other? A language can be endangered even if it has several hundred thousand speakers. If the people using it among themselves are all adults, the language is in trouble no matter how many speakers it has. And, of course, their is the unanswerable question: if today's kids speak the language, will their kids still want to speak it?
Fifteen or twenty languages have been brought back from extinction. The most impressive example of this is Hebrew (Hebrew wasn't really meaningfully extinct... but, before the founding of the State of Israel, it was used only in religion. Across the centuries, many Jewish children learned Hebrew so they could read and speak the prayers, but people didn't speak it to each other and it didn't have the vocabulary to talk about things not mentioned in religious writings). Today there are 5-6 million native Hebrew speakers. The language is unlikely to disappear. However, other revived languages have much dimmer outlooks.
For languages with relatively small numbers of speakers, isolation and ideology (often in combination) are factors that favor language preservation. Groups that are sufficiently large and geographically isolated are likely to be more successful at holding on to their languages than those that live in close contact with others. However, ideology is probably the most important factor. Religious communities such as the Amish or Hasidic Jews retain language while living within 50 miles of some of the largest cities in the US (or, in the case of some of the Hasidim, living in New York City). The importance of ideology poses a strong challenge to many small languages and revived languages. Wampanoag is a Native American language that was extinct by the end of the 19th century. It was revived in the late 20th century and it's first new native speakers were born in the 2010s. Today, it has a few dozen speakers and perhaps a few hundred more who are trying to learn the language. Will Wampanoag survive into the 22nd century? That depends on the ideological commitment of the children, grandchildren, and great-grandchildren of the people currently learning the language (and to a lesser extent, the continued willingness of various individuals and institutions to promote Wampanoag classes). We can't know anything about these factors decades from now. We can say that projecting Wampanoag into the 22nd century will be very challenging.