I would wager that an employer would just shift their office overseas, rather than be forced to increase wages. See what happened to manufacturing around the world.

By and large, I think its a quid-pro-quo between the US wanting foreign markets to sell into, and other countries wanting to sell their products, as well as human-resource-services into the US market. But, the US is a saturated market, and so the only growth is in emerging markets. Which also translates indirectly to 401(k) growth...