The US military spends like $1 trillion a year and you say they can't afford to go back to the moon?
What would it cost? A few hundred million $$? Thats nothing in the total scheme of things.
Not to mention NASA have launched spacecraft to go explore other parts of space, so obviously they have money.
The entire Apollo program cost more than 25 billion dollars. in 2009 they estimated the cost for the same program in 2005 dollars to be 170 billion dollars. As of 2010 it would have cost 18 billion dollars for just one landing. The 2012 NASA budget was just over 18 billion dollars total.
The military may have a trillion dollars in their budget but since NASA is not part of the military, they have no access to those funds. It would take the politicians in Washington allocating more money in the federal budget for NASA to get more money.
So yes I believe it is lack of funding and the numbers back me up.