By long established Federal law, recognized by the courts, when you come to a Port Of Entry into the United States from a foreign country you are not in the United States until your have been admitted by an inspector - so - you are not yet under the protections of the Constitution.  You may be an American citizen but you are NOT yet in America.   Your person, property, personal effects, everything, is subject to a search, IF you want to enter the United States. Once the inspecting officer 'admits' you then you come under the protections of the Constitution (which nowadays doesn't mean jack to the Government, unless you're ready to take a few lives to protect your rights).

"The government has a sovereign right and responsibility to secure the borders."

Nice.  I like concise bible verses. 

First, if you have personal data on your laptop, and you do, you must have whole disk encryption.  This includes encrypting the swap partition, and the root partition should be encrypted separately from your home partition.  This acts as a flag against a key logger gaining the single passphrase protecting them both if they are encrypted together.

Second, private data requires physical security as well as software security.  The best and easiest way to keep your data from criminals (both official and unofficial) is to keep them physically separated from it.  In a situation like a border crossing, this means you also should be physically separated from your data.

This can be done several ways, but the two most used would be to encrypt the data in a container that is stored and retrieved via network, and/or sending the hard drive to your destination via other transportation than you are using.

But warrantless wiretapping, recording of all emails and internet traffic, requiring ISPs to maintain logs of our traffic, naked body scanners, sneak and peeks, no-knock warrants and everything else are just fine.

The Grey Lady is senile. Put her down.