The answer may not be the governments problem to solve properly. This is America, a capitalist, competition based economy. Why not allow bidding to occur on contracts to defend the border. Private companies provide all kinds of military support to our government, the range of power to enforce the border would require strict controls against conflict with local, State, and Federal law enforcement.
Call Halliburton or one of its subsidiaries, Kellogg Brown & Root, maybe? That would make the leftie-liberals just NUTS.