The 10 most commonly prescribed medicines on the British NHS are:
Simvastatin
Aspirin
Levothyroxine sodium
Omeprazole
Ramipril
Amlopidine
Paracetamol
Salbutamol
Lansoprazole
Atorvastatin
That's 4 developed in the US, 3 in Germany, one each in Sweden, Japan and the UK.
But that's not the important thing here. What's important is that all of these patents are expired. That's not a weird freak of the UK. Most of the drugs prescribed everywhere are no longer under patent.
But even that's not the important point here. Prescription drugs do not explain the huge disparity in the cost of healthcare between the US and the rest of the world, since they only account for 7% of US healthcare costs.