There could be cultural issues at work or unconcious bias on your part. I work daily with people from other cultures and the potential to be misunderstood is great.
Americans, unfortunately, often have a cultural bias that they are number 1 and everyone else is somewhat less good than they are and it comes across to the people they work with as arrogance (which it actually is, but more a cultural arrogance than a personal one). So check to see if you consult your American co-workers and listen to their input but dismiss the input of people from other cultures, for instance.
As far as what specifically to fix, you need to ask first your boss and then your international co-workers. If your boss has told you that you have communication issues, ask for specific examples and then listen to why they were considerd to be a problem. You need to do this without getting mad or trying to justify.
After your boss gives you the specifcs of what complaints have been made, then pick one or two people from each of the cultures you are working with and go to them and say that you have been told you have a problem communicationg and you need to understand how people in their culture prefer to communicate and how they expect things like emails, business meetings, casual conversation to go.
There may be issues with you standing too close or too far awy. They may prefer a more indirect communication style (I had to get used to this with my Indian colleagues). They may prefer to have information flow differently - Americans tend to go directly to who has the information, some other cultures prefer to go through the management chain of command and if you skip the manager and go to the worker, he will be insulted. They may think you talk to fast or have an accent they find hard to understand. They may think you are too personal in what you talk to them about casually or not personal enough. It ireally is hard to say. The only people who can tell you are the ones currently who have a problem with how you communicate.
If possible, I would look for some reading materials on the culture of the people you work with. Try to get a better understanding of where they are coming from.