When you practice this tip, you won't be able to speak English like a native speaker forever, but it will give you a small idea about the American Accent.
Follow these steps in order to realize it:
1-Find a short sentence being spoken by a native speaker (MP3 file if you can)
2-Listen to the MP3 file many times.
3-Try to speak exactly like the native speaker.
4-Practice it many times up to the point you speak like the native speaker.