Tom Coburn is not a liberal either even by European definition, under which even that there is a different between liberal and conservative. You don't see Coburn fitting well in the Liberal Democrats or Democrats 66 even economically do you? A European economic liberal would be like Mark Kirk (at least before he started running for Senate and got all teabaggy.)
Obviously Coburn wouldn't fit well in a liberal party, but nobody's calling him a liberal. His economic policies, howeber, are extremely neoliberal.Far right economically != neoliberal. Lots of extremist libertarians hate neoliberals. I know Bono does.