Often the question is posed of how to learn a language if one is not ready to travel. This is the wrong question to ask. Learning a language is entirely possible without immersion, even to a high level. The most important aspect of language learning is to have the right attitude and to be persistent. Because of this, the converse is also true. If someone is not persistent, immersion will not help.
That being said, immersion can be a useful supplement to a good language learning routine. There are many benefits to immersion, even though access to immersion is not what determines success.
The top benefit is probably motivation. This may be surprising to some, especially those that think learning is impossible without being immersed. The truth is, unless you’re learning a very rare language or you live somewhere without libraries or computers, you already have everything necessary to learn. At this point, it becomes more of a question of motivation. Being in an environment where you can immerse yourself can reinforce the fact that your target language has many uses and you can find a way to use it that interests you. This is especially true if you are in a place where it is the main language. However, it can also be true if you only have a kind of soft immersion where you’re surrounded by media in the language. Seeing the language used and having the opportunity to take part, for many people, can make a huge difference in motivation compared to learning for a more theoretical purpose.
The benefit of immersion probably most typically thought of is real life practice. For common languages, you can find plenty of authentic content without being immersed. However, immersion still improves the variety of content and makes it more interactive. It can help introduce you to vocabulary that may have taken longer to encounter by just finding media yourself and experience a wider variety of contexts.
Cultural experience is another benefit. Although you can learn plenty about culture on your own, being in an environment where the language is naturally encountered can make this process more efficient. Although you can definitely learn a language without actively learning about the culture, it can make the process more interesting and can provide context that can be useful when it comes time to use your target language in real life.
Immersion can provide a boost in motivation and help the language learning process move along more naturally. However, it is very important to remember that anyone can learn a language from almost anywhere. You can experience all the benefits of immersion right now if you put your mind to it. You can educate yourself about the history of the language and the culture around it if you need more motivation. You can find authentic content and expand the topics you read about to get broader authentic practice right now. Immersion can be a great opportunity, however, it’s important to make sure you are already taking the opportunities you have.