I don't know if any of the following has/is being done to prevent terrorists attacks on the US. I know that I would like to see steps 1 through three taken, even though they would be
painful at first.
1. Stop the import of oil. Typically, acts of terror are performed within close proximity of the target - and that takes money. Money for passports, money for visas, money for plane tickets and transportation, money for housing, money for training, and money for supplies. Taking away the revenue supplied by middle-eastern oil exports would greatly reduce the funding available to terrorists, which in turn would make targeting a country halfway around the world more difficult.2. Outlaw the manufacturing and sales of internal combustion engines fueled by petroleum. Is this an extreme step? Yes, but no more extreme than invading two countries. Use this step to reinforce the actions of step one, because let's face it, we can't produce enough oil to satisfy our own demands. Naturally this step would have to occur over the course of two or three years to ease the blow to car manufacturers - they would need a heads up to get into other industries. 3. Move toward green energy. Eliminating the production/sales of gas/diesel fueled engines would create a huge demand for alternative energy sources. In order to persist with steps one and two above something would have to fill the gap, renewable energies would be the logical choice. 4. Background checks for visas. No more "quick" visas, require a background check (in their country of origin) of any one applying for visas from the countries in question. If their own government has any dirt on them, deny the request up front. Pass the cost of this background check onto the visa applicant. 5. Limit the number of visas issued to Arab nations (i.e. the countries in question). Limit our exposure to the threat. Lower the number of visas issued to an amount where the visitors could be easily tracked. 6. Visitor Registration. Require visitors from these nations to register with a federal agency: phone numbers, addresses, email addresses, schools, universities, etc. If any of their information changes without receiving approval from the agency first, revoke their visa immediately and notify all law enforcement agencies that these folks need to be tracked down to be exported. 7. Fingerprinting. Require finger printing for visas to the U.S. from the countries of concern. Many of their names are very similar, that can make things confusing when we're trying to keep track of who's who. Having a finger print file to reference would statistically reduce confusion in this area. 
A plan for peace...
