So this assumes that most of the the prospective component companies themselves are not very competent, and that their size and leverage from the dominant units

So this assumes that most of the the prospective component companies themselves are not very competent, and that their size and leverage from the dominant units is all that gives them market power. That, I think, is probably a pessimistic view - Gmail being split off from Google Display Ads and Google Search wouldn't make me any less likely to use Gmail, say. But it would also open the door for US companies to replace them, not simply foreign ones. It's not like countries that crack down on the US services have produced many better companies good enough to compete in the US to date. I'd accept the risk of some new dominant players from other countries in exchange for limiting the risk of misuse of market power and increasing the chance of new US competition to arise. Competition from inside or outside the US should make the encumbents better. Stagnation is what will let them be replaced by disruptive newcomers. EDIT: I think a more likely risk is that we lose some money-losing "free" services that are basically loss-leaders, maybe even some vanity project ones. I would LOVE to replace some of those with paid products that a more healthy company could grow around, with better user-facing incentives.