There are two ways to secure internal air travel in the US.

1) Secure the borders.
Put an effective defense that can stop *most* terrorists from even
getting into the US.

2) Use the TSA to treat anybody and everybody as a terrorist.

From the Obama administration point of view #1 has two problems:
A) Cost. The Israeli fence around Gaza that stops suicide bombers
cost only a million dollar per km. A similar fence between the US
and Mexico would cost, for 3,000 km, about $3 billion. The TSA
cost about $7 billion per year so an effective fence would mean that
the Obama administration will have $4 billion less to spend as it
wishes.
In addition, the fence will be built by private companies after a
competitive bidding. Not much opportunity to get some jobs for
friends and family of those in power.

B) Power. The TSA is about power. Either you let them sexually
molest you or you will not fly. It is that simple. The only exception
is people that the administration likes, AKA VIP. You may feel
that the government is too intrusive and vote for the Tea Party,
but the Obama administration will get to molest you in the air
port and teaches you once and for all who is the real boss.
Why would Obama give up this kind of power?