How can I become less affected by politics?
This is an easy one. Stop looking at the media so much. The media is not reality. It's a small negatively skewed snippet of it. There is so much more to life than the perpetual negativity we see in the media. 

It's only in recent times that the media has become way more invasive. 
We now have 24/7 news cycles and people walk around addicted to and staring at devises all day. All that negativity is going into your mind and colouring your world view. It pretty much works the same way as porn. People are addicted to the dopamine/adrenaline hit they get when something in the media fires them up. 

The politicians thrive on dividing people. Refuse to play into their game. Stop watcing it just for a few days and notice how much calmer you feel.   It's good to stay informed about important world issues but that but does not mean habitually checking the media every 5 minutes or even everyday. If Kim Jung is about to launch another missile what can I do about it?? Nothing!! So why do I need to know about it? So I can go on Facebook and rant? I don't need to know. It's pointless. Far better to use your energy in effecting real change where you can. 

You will need to break the habit. It's the only way. If you continue to look at that stuff on a daily basis it will continue to colour your mind in that divisive angry way that only politics can do.  Let go of it. You don't need it.