That seems false. What do you mean when you say they're fundamentally identical? It would also help if you were clear about what you mean by 'conservative' and 'liberal.'
IMO,In primary respects there is no difference between a libral or a conservative.
The terms "Left and Right," come from the British House of Commons, where the Popular(Liberal) parties have traditionally sat to the left of the speaker and the Royalist\Aristocratic Parties(Conservative) to the Right.
As you already probably know in the 20th century US, Democrats were considered the Liberal party, with an agenda of individual liberty, Civil Rights and economic policies based on promoting general prosperity.
While the Republicans pampered an authoritarian social agenda, and based their economic strategies on the promotion of Big Business interests.
In the 1960s those labesl started breaking down with socially and economically Liberal Lyndon Johnson committing the US to the Vietnam War and by the end of the Reagan-Bush Era those distinctions were pretty much gone.
Racial and class politics have become more of a factor and "pure" Liberals or Conservatives are difficult to find. Blacks and Hispanics can often be found in the ranks of social conservatives when their own groups are not involved. Many economic Conservatives are socially Liberal these days and recently social Conservatives are pushing some very Liberal Economic policies.
I beleive the days of easy labeling are gone. You have to look at each representative individually, and then on an issue by issue basis. The old adage of, "Never write anyone off," is more true than ever. Single issue coalitions have formed around leaders who would never have been seen sharing the same platform 20 years agoand it's going to get more confusing, not less.