First of all, it won't happen. The US would get hammered by international opinion if we jacked-up tarrifs. Besides, Libertarians and neo-cons would be in the front of the protest marches against any such action because they don't want to pay $10 more for a PDA but would rather see their neighbor laid off and begging for bread.
There is another problem with "tariffs". They really only apply to manufactured goods and not intellectual property, which is what IT jobs really are. Let's say that Microsoft laid off everyone of their developers in the united States and hired nothing but Russians and Indians. So this goofy-looking OS comes back, riddled with back-doors, security breaches and enough bugs to keep the Russians and Indians forever employed "correcting" the problems; they could still sell the shrink-wrapped software without tariffs. Actually, because of our stupid laws regarding the exportation of encryption technology, it would be in Microsoft's best interest to develop all of the crypto outside of the country so that the foreign made code would be exempt from the ban. Our government has placed too many laws and restrictions on domestic business to ever provide for a silver bullet solution to the outsourcing problem.
It is impossible to level the playing-field. The united States has too much infrastructure, too many dependant on entitlements, grants and aid, too many places for our military, too many economic demands around the world to ever be on the same level playing-field with nations whose idea of mutliple use technology is to use their dirt roads not only as transportation, but also as toilets and community recreation centers.
There is nothing about the importation of software that inherently makes it immune from tariffs.
And this would be different from the current Microsoft OS products in what way, exactly?