I agree with what has been said here and would also emphasize the potential benefits of sharing your perspective with eNotes students and sharing your expertise as well. As teachers, these are the two biggest things we have to offer, regardless of where we are from.
I agree with the third post concerning the benefits American students can receive from the observations of someone from a foreign country. Too many Americans suffer from the belief that the American Way is the best (and some would say the only) way, and students could certainly learn from the opinions and views of someone from your part of the world.
This depends a great deal on what the subject matter is. In many ways, it is very good for students in the US to see the opinions and views of people from other countries. This would be particularly important on topics that have to do with society or politics, but it would be welcome even in topics like literature.
I do not think there is any reasons that a non-American should be at a disadvantage.
I don't think that a non-native teacher is at a disadvantage in an online arena such as enotes. A couple of things I think would help would be to
1) Look at the age of the student and adjust your explantion accordingly. A high school student is going to have more background knowledge than a middle school (6th-8th grade). The older the student (i.e. senior vs. freshman) will be better prepared for a more complex discussion.
2) Give us much detail as possible when giving answers. I think this is important for all answers on sites such as enotes because the opportunity for follow-up questions is there but likely not to receive an immediate response. If you give too much information, the student will be able to skim through it quickly and get to what they need. The less prepared student will have to read the introductory information more carefully.
3) Since most of the posts are from high school students or first/second year college students, do a search for high school websites in the subject you are answering questions to get a better idea of what is being covered.
4) Look at other questions ro discussion posts being answered in your subject and you'll get a better idea of what other editors are saying and the depth level of their explanations.
Your students might enjoy using a free dictionary toolbar, which provides instant lookup of an English word without opening a dictionary or going to a dictionary website. Word definiton is shown in a popup box when the user clicks and hightlights a word on a web page, or enters it in a box.