Not the country as a whole, no, but if you have a concentration of people speaking a certain language it can be advantageous for a business owner to have staff who can speak that language to encourage that part of the customer base to do business with the company. If you want to learn a foreign language and you happen to live near people who speak a particular foreign language their proximity means you have an additional resource for learning that language.
We have people from all over the world coming to the US. We do business all over the world. I got one of my first jobs because I could communicate in French (I lived near Canada, so French was a fairly common language there). If I lived in a Chinatown and/or desired to do business with China I might consider one of the varieties of Chinese (see Mark Zuckerberg - also, if I recall correctly, his in-laws speak Mandarin so there’s an additional reason for him). If I lived in southern Texas Spanish would definitely be useful even if not required. If I had some reason to do business with Bulgaria taking some lessons in that language might make a lot of sense.
But if you just want to learn an additional language and don’t have a strong preference, Spanish is one of the mostly commonly spoken languages in the US after English, there is a lot of Spanish media available, you are more likely to find a Spanish speaker than someone who speaks, say, Finnish or Swahili, and it’s frequently offered as a language course in many, many places. Thus, there are a lot of resources and opportunities for someone to use their Spanish.
But hey, I took on Irish Gaelic because I wanted to, not because it was useful. Some people learn Klingon, of all things. There’s a world-wide Esperanto community.
If you have a particular motivation for a language, no matter how obscure, go for it. If you don’t have a preference and live in the US Spanish is a good place to start.