Why is Christianity fixated on ancient Israeli culture? Is such a 'spacetime-lock' evidence of falsehood?

When I studied Mohammed's religion, I thought the insistence and enforcement of 7th century Arabian culture (e.g. diet, clothing, marriage, law) on the entire planet unreasonable, and evidence it was false. "The creator of the universe would not cause such diverse human experience only to insist that everyone adopt the culture of one region a millennia ago," I reasoned. Yet I find Christianity doing basically the same thing: I sat in Mass today and realized the Japanese were reciting an Old Testament passage about 'the cedars of Lebanon' and the Israeli exile to Babylon (what, 587 BC?), despite the fact that likely no one in that church had ever even *seen* a Lebanese cedar, and likewise that exile more than 2,000 years ago has nothing to do with them today, or any relevance to the Japanese at any point in history. I realized that the Catholic Church is pushing ancient Jewish culture on people worldwide in the same way that Mohammed's imams push Arabic culture on people worldwide. Why does God want us to fixate on that region at that point in time? How is that good for mankind? How is it relevant for us today? Why is it not evidence that the Christian faith is unreasonable and the Bible obsolete?