In America, there are 231 million people who speak English as a first language, and 37 million who speak Spanish. The next-most-common language is "Chinese", with 2.8 million speakers, but that is fairly evenly divided between Cantonese and Mandarin, and the two are very, very different from each other. French, Tagalog, Vietnamese, German, and Arabic all have over a million speakers in America. They usually have very different proportions in different areas. If you are planning to move to Miami, Haitian Creole would be very common. If you are planning to move to Minneapolis, Somali would be quite common. Overall, though, the vast majority of people in America will have at least some familiarity with either English or Spanish. So, think about other ways the language could be useful. What field do you work in? Stereotypically, if you are an engineer, you might want to learn German or Japanese. If you are a chef, you might want to learn French or Italian. And so on.

I would decide on a language you like, rather than a language you feel will be useful work-wise now. All languages bring benefits and you never know what direction your life takes, so a language you think is not useful today may be very useful later. For this reason, I'd recommend choosing a language that you like. One you like the sound of, or one whose culture you'd like to know more about. Perhaps narrow down the language further by how easy it will be to practise speaking it immediately. Much easier to learn to speak a language when from the beginning you can practise it in person by going to that local cafe or locality where you know that language is spoken by some. Easy then start up a simple conversation and gain some practice.