This depends on the question that you are answering with the essay or the specific assignment that your instructor gave you. If your essay is supposed to be completely fact-based, then you should keep 1st person out of it. However, there are times when essays will be a hybrid between personal and academic essays. This should be clear both from the content of the class you are in and from the assignment your teacher gives you. It will usually be in a humanities type of class that will allow for personal examples or opinions. If you are in doubt, talk to your teacher. Most teachers want their students to succeed. So, if you ask for clarification, then you will probably get it. :)

In an American academic essay we do not write in the first person. Let me know if I can help in any way. :)

Caution: I'm not a teacher and I don't grade essays. Yes, it is safest to keep it impersonal and dangerous to use the words "I" or "we." This will happen automatically if you "let the facts speak for themselves." What they are looking for is your ability to state facts clearly and put them into a meaningful pattern.