[I]s graduate school necessary if I want to go into an advanced field like AI? Are there any paths other than graduate school which I can use to get into the career?
"Go into AI" is pretty broad. What sort of job do you want to be doing? Theoretical research? Software development? Engineering? To get an idea of what jobs are out there you can look through the job postings at Google Research, Microsoft Research, IBM Research, Amazon Research, and so on. All of these do ML and AI.
They have position all along the spectrum from things that only require undergraduate degrees to things that require PhD's. I have no experience with the non-PhD path, so I can't tell you much about that, but a lot of their internships are geared to ML/AI PhD students spending their summers there, and then those same people get their degrees and apply for research jobs at those companies.
I am wondering what my college studies should look like in order to make my interest a reality.
I can tell you what is useful to know for ML and AI, besides programming: In computer science, you need to have a good grasp of the theory, taught in courses like Theory of Computation and Algorithms. Some schools also teach an undergraduate AI course. Machine learning can be viewed as the intersection between computer science and statistics, so basic statistics is important. A lot of AI and ML has to do with (mathematical) optimization, for that you need a good grasp of linear algebra and multivariate calculus. Some methods (like neural networks) require understanding differential equations and partial differential equations (but I would put those down as fairly optional, you'll learn the relevant material if you ever need to).
The reality is, if you are going to go to a graduate program in AI/ML, you'll learn all the AI/ML-specific things you need to learn there. What you need to know to get accepted into the program is very variable on a program-by-program basis, but the reality is that the coursework probably won't be the most important thing in the admission process. If you're going straight for a job out of college, employers probably won't care much about your coursework either. It will be all about how you do at the interview, which will be very variable on an employer-by-employer basis.
At the end of the day, my suggestion is to think about what job you want to end up doing and work backwards from there to figure out what you need to do to get it.
