It is true that teens can be cliquish, choosing to hang around with the same people all the time. Admittedly, it can be difficult to make new friends during high school - but it's not impossible. Keep in mind that you'll be graduating soon and either be embarking on college or a job so you'll definitely be amongst a new pool of people where you can make new friends again.
In the meantime, don't spend too much time reading into this situation. Just because you're feeling lonely now doesn't mean you'll be lonely for the rest of your life. Keep up with your studies, nurture other friendships -- even if they aren't close ones, stay in touch with your friend in Shanghai, and try to put yourself in new situations where you can meet other people.
Living in a small community or attending a small high school can limit opportunities to make both girlfriends and boyfriends. Can you join a gym? Find out whether there are any community service activities available through your school? Can you take an adult education class? Volunteer at a hospital or agency in your community? Perhaps, you'll be able to make an older friend or make friends with a guy.