How compatible are (Theravada) Buddhism and the Western life? There are a lot of people practicing their religion at home (to some extent). But how practical is that for a Buddhist?

My question came boiling up when a family-member said that I ultimately have to choose between 'my western life' or becoming a Monk because they think they aren't compatible and to be honest, I don't really know.

I feel myself to become quite less social when I practice Buddhism which is by my knowledge a common reaction when you get to see things as they are. The Vinaya Pitika describes 227 rules to ordained Monks for the sake of becoming enlightened. There are many distractions which keeps you from the right path and you will break 220 on average each day.
I woud say Theravadan Buddhism is compatible with the West because it is already happening. Jack Kornfield studied with Ajahn Chah and then went on to found the Insight Meditation Centre which is partially inspired by this practice (though doesn't wholly identify as Theravadan). Ajahn Chah's lineage itself has come to the West with the  Thai Forest Tradition and to quote from here


  They provide centres for monastic training, as well as, teaching and
  practice for the lay community.


So you don't need to be a monk to practice. My own group the Triratna Buddhists are also very influenced by Theravada Buddhism and we have no concept of monks. Even order members are considered to be lay followers. 

As Buddhism moves Buddhism changes. As it moves into the West and as Western culture influences into the East then (Theravada) Buddhism will change. But Buddhism will always teach liberation - how could it be any other way. So I would humbly say that yes you can practice but the practice might not be quite as it was before.