1) Demand that commercial airliners create, install and consistently enforce an impenetrable door to the cockpit, so that no commercial airliner could be successfully hijacked in the future
2) Use all our foreign intelligence and influence with foreign law enforcement to aprehend Osama Bin Laden.
3) Massively increase the amount of investigation for any and all people entering the USA from any nations suspected of harboring psychotic terrorists - up ton and including refusal of entry for people who do give us any reasonable cause to believe they might do harm to the USA after entering the country.
4) Withdraw our overt military presence from any country which is not completely, 100% paying the entire freight for said presence.*
That's pretty much it.
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Under GW Bush's oversight, #1 was pretty much taken care of pretty quickly.
#2 was supposedly implemented, but clearly has been either unsuccessful or aborted
#3 has hopefully been implemented, though I have no way of knowing how well
#4 of course was not and will not occur under either GW Bush or BH Obama.
*And if President, "I" would have already done it in the first eight months of my term in 2001 before the events of 9/11/01 even occurred.
NOW, aren't you glad that in fact, "Barman" was not POTUS in Sep 2001?