Why are service intervals in the US generally shorter than in UK?

Why are service intervals in the US generally shorter for the same car than in UK and Europe?

My diesel car has an 18,000-mile servicing interval, is this too long to leave it?

I have a Renault Kadjar diesel, which I'm told needs servicing every 18,000 miles. I'm a bit uneasy about this. I had Skoda diesels previously that I took off longlife service intervals and did every 10,000...