I don't think it's reasonable for U.S. lawmakers to have an opinion on what Apple's competition should or should not be expected to do in order to compete with Apple. As I've said previously, if Apple was able to build it's own phone and OS in order to compete with RIM, and Google built its own phone and OS to compete with Apple, there's no reason why sufficient market pressure wouldn't attract the investment required to do it again. Regulation is simply forcing the situation when this pressure doesn't seem to exist. If users cared that much, they would buy Android. They don't. And since they don't, it's completely unjust for their representatives to apply force.

U.S. lawmakers are elected by U.S. citizens to represent their interests, which are not necessarily aligned with Apple's interests. In the case of Apple abusing its monopoly/duopoly power to extract higher fees from developers that are ultimately paid by users, these interests are not aligned. Lawmakers in any country have an obligation to introduce measures that prevent private companies from denying people the option of taking actions (such as sideloading) that would serve their interests, even if they would be counter to Apple's interests.

Monopolies and uncompetitive markets (such as the mobile app store duopoly in many regions) result in deadweight loss,* which hinders the growth of the economy at large. Lawmakers in any country would do well to increase their country's economic efficiency by limiting the ability of companies with high market power to distort the market. Uncompetitive markets are not free markets.

* https://en.wikipedia.org/wiki/Deadweight_loss

Is there any action taken by U.S. lawmakers that you wouldn't consider an overreach? Apple is also a U.S. company composed of U.S. citizens who should be at liberty to make and sell whatever devices they see fit. U.S. lawmakers should act primarily in defence of that liberty.

> If we will not endure a king as a political power we should not endure a king over the production, transportation, and sale of any of the necessaries of life. -John Sherman

I hardly see how Apple, by taking 30% of revenue from substantially games, is king over the production or sale of any of the necessaries of life.

Apple is just one company among many in the U.S., and there is no legitimate reason for lawmakers anywhere to prioritize Apple's ability to restrict other people's liberties to the detriment of everyone else's liberties, especially liberties that concern everyone else's own property (such as sideloading). Apple will still be able to make and sell whatever devices they see fit, that ability is not in question.

The Commerce Clause* of the U.S. constitution empowers lawmakers to regulate interstate commerce. This clause has enabled the passage of antitrust laws in the U.S., including the Sherman Antitrust Act and hopefully the upcoming Open App Markets Act.

* https://en.wikipedia.org/wiki/Commerce_Clause