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