Clinton, Bush and Obama could have all done more to prevent terrorism. Obama is the one currently making a mess of it.
The army dropped the ball on Nadal. There were indications the guy was going jihad but the Army higher ups were so cowed by the fear of being labeled islamaphobic they ignored the problem. It was Nadal's fellow psychiatrists that reported something was wrong but they were ignored. This is an example of what happens when the pressure of political correctness results in serious harm. The Muslim rapes scandal in Britain is another.