What is un-american? Is it difficult to define? Who gets to decide what un-american is?

I believe un-American is not following the laws of America. There are laws for the citizens and even visitors/tourists that we have to follow and obey. An American is taught from youth to obey the laws America has made and are forced to follow them by law. To follow the laws of America is an American custom and a necessity of a citizen. Some say it is difficult to define what un-American is and I agree. It is difficult to define what un-American is because different people have many different opinions on what un-American is. But to put it simply, being non-American is not being American.  Americans get to decide what un-American is, since they're American. They get to decide what's un-American is because they have the right to have freedom of speech, so they have the right to say what's un-American and what not. Freedom of speech is a law, which American’s follow and obey.