"Radical in the White House" was published in the New York times on January 21,2009 and was written by Thomas L. Friedman. Friedman, I'm guessing, is a fellow American and by this being published in the New York times, it was read by many people which no doubt was one of the goals for the article.
The American people is obviously the audience he was shooting for to read his publication. In my humble opinion, he wrote this article to get a reaction out of people, some feedback, and also to restate what is already known and been argued about continually. He writes how, to put simply, Bush was a crappy president and Obama needs to do a good job or America is going to fall apart at the seams. The reaction he most likely received was a just slightly updated version of the peoples attitudes and reactions throughout the election, the difference is, the outcome of the president is known. I'm sure there were some good, Obama followers, and some bad, Obama haters.
He unconsciously states a message to Obama from the American People. "Good luck, we're watching carefully, and if you mess up we'll tear you to shreds."