In Little Brother, the protagonist, Marcus Yallow, is tortured and humiliated by the Homeland Security service, rather than protected by it. This leads him to vow vengeance on them, and the plot proceeds. He manipulates the Internet systems to do his bidding, and in the end gets the aid of adults to shed light on the excesses being done to ostensibly make safe the USA.
In The Sixth Column, written in advance of the attack on Pearl Harbor, the Pan-Asian Union attacks and defeats the US, and they occupy the nation. One secret laboratory has discover a ray that can, when manipulated properly, transmute elements, and kill specific races of people. The survivors of the lab's research team, led by an advertising agent, recruit secretly, and overthrow the invaders from within the nation.
Why did these books seem so similar to me? In both, race was a factor, shown by Jolu and Van and how they react and are treated in Doctorow's book, and by the way the Asians treat Caucasians, and vice-versa in The Sixth Column. In both, a seemingly overwhelming force had taken over the familar territory from outside (the former from Washington, D.C., the latter from Asia). In both, use of a technology, in Little Brother, familiar and plausible, in Heinlein's novel, magical and unlikely, leads to the defeat of the force. They each had a feeling of unease, as the underdogs were constantly on their guard.
I found in each deep fascination.