Is that a large amount of the US domestic production is due to foreigners. Illegal mexicans account for over 20 billion dollars worth of domestic economy. If you add up the domestic production, property holdings, businesses of foreigners, it's a chunk of change. If you add in foreign investment in stocks (US businesses), that number gets really big (a lot of zeros on it). Then you add the technical contributions, that is the future.
The US is already suffering due to the stem cell policy, where Britain and China are benefitting from the policy.
I don't think a closed door, reclusive policy is the best.
But if you quit Kyoto, Quit WTO, Quit NATO, Quit the UN, Quit Exports, Quit Imports (Oil included), Stop international flights, man the border with a million peeps with guns(both borders), shut down the harbors, block all international telephone calls, block international internet connections it could be done. Not sure if anyone would miss anything, like electricity or oil, but then you could stop all possible threats.
Granted you couldn't drive (no oil), watch tv, use computer (electricity imports), eat (farm labor costs), but you would be finally safe!
