Here in the US, MINI gives a 4 year/50,000 mile (Whichever comes first) factory bumper to bumper warranty. In addition, we get free paid scheduled maintenance for the first 3 years/36,000 miles. This is basically the same warranty as the more expensive BMWs.
I am not sure why this varies from country to country, I suspect it has to do with marketing schemes, costs, industry standards in said countries, etc.
I think in the UK, MINI drivers also get a 2 year warranty.
Also consider that it is very difficult to sell a new car in the United States with a warranty shorter than 3 years. The standard here is at least 3 years/36,000 miles. 4 Year/50,000+ mile warranties are issued mostly to high end cars. Some budget brands such as Hyundai, Kia, Suzuki offer 10 year/100,000 mile warranties to be able to move thier questionnable metal out of dealer lots.