I know several programming languages (e.g. Elixir, Elm, Erlang, Haskell, Ruby, Python, etc.), and I also speak English and Japanese fluently. With programming languages, the fundamentals beneath the syntax are basically the same. For example, whether I use recursion or for loops, all of the programming languages I know support iterating through a list of data. Similarly, they all have some mechanism for making logic decisions, such as if or case statements. So, learning a new programming language is just a matter of mapping new syntax to concepts I already know. If learning a new spoken language were simply a matter of mapping vocabulary words to meanings, then I would say both are the same, but this is not the case.

In spoken languages, there are cultural differences that have to be learned and concepts that just don't translate well between languages, if at all. Idioms are also difficult. Often times, there is no cultural foundation in one language to make sense of the idioms used in another. Unlike computer programming, there is no underlying base that you can use to map new knowledge too. You have to build your entire understanding from scratch.