I believe the grandparent is referring to the US Senate, which was designed as the state's representation in the federal government, and where each state gets 2 senators.

This means that California gets 2 senators but so do Iowa, Nebraska, Kansas, etc.

Now, the conclusion of the grandparent does not follow in my opinion.

Nothing in the constitution mandates the current state boundaries. California could break itself into multiple states (there is a population minimum) and gain more representation in the senate if it wanted.

But there are trade offs. California is a huge prize in the electoral college and has been a safe Democrat win for quite some time. Splitting into multiple states could jeopardize that. Being large also allows them to lead the way on regulation in a way that smaller states couldn't.

The US government is quite the game theory problem.