Your predicament is not uncommon, nor is it hopeless. Countless college grads go through this and the ones who are determined enough find a way out of it. You have just as much of a shot at turning things around for yourself so long as you proceed from a mindset of problem solving and a willingness to work like crazy for whatever it is you want. Here's a fill in the blank statement and a question for you: "I want ______. Now what do I need to do to get there?" I would invite you to answer the first part of that statement, and begin looking for solutions to the second part.

Personally, I have a very hard time believing that the job you currently hold cannot somehow help you in the future if you leverage it correctly. I'd encourage you to identify what sort of value your current job is giving you rather than focusing on all the things you hate about it. Just because you don't find your current job and skills to be noteworthy(I'm assuming its because you don't enjoy it) does not mean that many other people will not. The larger picture is that businesses and companies find people with international experiences and skills that come with it to be desirable. The job itself might not be noteworthy, but the fact that you are an American who possesses conversational reading, writing and speaking skills in Japanese is, and employers back in the U.S. will find that attractive in the future regardless of whether you ever end up needing them when you find work back home or not. If you were applying for a great job in the future and the company could only pick between you and someone else with the exact same qualifications, if the company is an international one and your competitor for that job position has no experience working abroad, the little tiny extra bit of international experience could tip the hiring decision in your favor. Stuff like that happens all the time.

As for entering into a different field of work, start networking, building relationships with people and expanding your knowledge and skill sets for that field of work. Especially if it is not currently something you have a lot of expertise and experience in yet. Knowledge is great(learn everything you possibly can though), but knowing and finding somebody who can help you get your foot in the door is often the first step a lot of people have to make to get to where they want to be. If you don't immediately know somebody who works in the industry, the best approach I have found is to begin identifying people who have the job you would dream of having and contacting to request an informational interview. People like to help people who show they are passionate about wanting to do something. If you present yourself to them appropriately and leave a great impression, they could very well end up helping you to find a job that gets your foot in the door somewhere, or they might refer you to other people who can. I did this sort of thing 2 months ago. 3 weeks later that same person whose brain I picked for advice on how to get started with entering the field offered me a very modest "get your foot in the door" position that will allow me to move laterally and upwards into positions that I actually desire within the next few years. It is far from glamorous, but it's a starting point, and I intend to climb. Perhaps you'll have to do something similar.

But I'm rambling. My point is simply that you should decide what you want and go for it full force. And be warned against ever choosing to settle for something or saying "good enough". You'll never even get close to feeling satisfied with your life if you do.

Best of luck.