Rob Yeung's Answer:
If even your boss is approaching your offshore counterparts directly, it's worth having a frank discussion with your boss to see what the issue is. If you have relatively recently been hired into the role, then presumably at the time of your hire your boss thought that you would have some value to add.
So it sounds to me as if your boss is the critical person who can help to resolve the situation with you.
Pursue your boss to get a one-to-one meeting in which you can discuss the issue. But before you enter into the meeting, make sure you recall to mind specific examples of what you believe is happening. In preparing to share your side of the situation with your boss, make sure that you use "I feel" statements to describe how you see the situation. Using statements in the second person such as "you do X" or "you do Y" sound so much more accusatory and could put your boss on the defensive.
Once you have shared your thoughts, get your manager's thoughts on what you could be doing differently. It is possible that there is some gap to do with your skill, knowledge, or even attitude that is making it easier for your colleagues to work directly with each other rather than working through you.
Other than that, I would avoid going into the meeting with preset ideas of what you want your manager and colleagues to do. You are the new person and you need to find ways to fit into the team – not to change and "retrain" all your colleagues to work in ways that suit you, the new kid in town.
I wish you the best of luck in your discussions with your boss.