Is it easy to learn an accent? No, definitely not. Otherwise, everyone would sound the same. It takes a lot of motivation and determination to overcome the natural pronunciation patterns hard-wired in your brain, ear, and tongue.
Many of my clients have been living in the United States for years, and yet, they still have difficulties being understood. A lot of this comes down to listening. If you are not discriminating the American sounds correctly, you will not be able to produce it correctly. Therefore, the first step to improving pronunciation is to simply listen. Pick a sound that you often say incorrectly. Study the differences between how you produce that sound, and how the sound is made by native speakers. Listen to the contrasts between them.
For example, many languages do not have the English 'TH' sounds. Due to this, many speakers use a /d/, /z/, or /s/ sound in place of the 'TH' sounds. Doing so leads to an accent because you are deviating from the correct way to produce the 'TH' sound. Listen to the difference between saying a /d/ on 'the' and saying it correctly. Are you taking 'duh' time or 'the' time to listen?
Listening to the sound differences is the first step to learning an accent. Without that, you will not become aware, leaving you with your native accent when you speak English. You also must get comfortable listening to yourself. If you don't like how you sound, and you don't want to listen to yourself, how will you improve your speech when others hear you talk?
Changing your accent takes time and practice. It will not happen overnight. But if you are motivated to learn and listen to yourself, it's an enlightening experience which will only benefit your speaking skills, and hopefully some other aspects of your life.