In America, the majority of the country self-identifies as middle-class, and in conversation and political rhetoric we basically use it as a synonym for "normal people." Not that the UK is wrong, but I think our usage matches the name a bit better. Doctor/lawyer-type professions are a bit exclusive to call them the middle.

If someone is trying to pull statistics, "middle class" is defined by income to usually be either the middle 3 quintiles (60%) of the population, or an income between $25k-ish and $200k-ish. Doctors, Lawyers, etc. are usually on the top end of that range, and called upper-middle class.