Honestly, 10 minutes with Wikipedia would answer this question better than almost everyone here. There are very few people who know the US and UK medical systems extremely well... Here's a shot however.
US: Undergrad = 4 years, med school = 4 years, residency = 3-10 years. For a general family medicine style doc, residency = 3 years -> Total = 11 years.
UK: No undergrad, med school = 5-6 years, residency = 5-9 years. For a GP, residency = 5 years -> Total = 10-11 years.
In terms of health care systems, US and UK are vastly different.
US: Crazy ass mix of private and public health care. Medicaid covers the very poor and many children. A sizable variety of private insurance companies cover almost all <65 years olds, 65+ have Medicare, but also some have "private" Medicare or private supplemental plans. Doctors work for "fee for service" which means that you get paid to have an office visit, do a surgery, interpret a test, etc. Payment comes from a large variety of payers from the actual patient to the federal government. Pay itself depends on a doctor's productivity.
UK: All health care related issues are covered by the National Health Service which is a government operated entity. As such, all doctors work directly for the federal government. Pay is not dictated by services, but is a salary (or perhaps by "hours worked"). The NHS covers health, vision, and dental care. Only about 8% of citizens have supplemental insurance. This would cover things like experimental chemo or maybe an elective joint replacement, i.e. things that the NHS wouldn't provide.
