The Senate, yes. But it's also not quite right to describe the apportionment of Representatives as strictly based on population either, or if that's meant to be the case it isn't handled well. They
only have 435 seats
to divide on the House, and no state can have less than one representative, and the formula we've been using for apportionment since the 40s further widens the gap by deliberately favoring smaller states by rounding up the apportionment quotient whenever it exceeds the geometric mean of the two nearest whole numbers; though not as blatantly as with the Senate, this still advantages tiny states and disadvantages -- well, mostly New York, California, Florida, and Texas, the four states where more than a fourth of Americans live but where people's votes are most blatantly devalued. The advantage is only to the tune of around 3-4% to the smaller states, but the more tiny advantages you throw on to the already existing pile, the more shenanigans become possible. You can read about the issues with apportionment, which I've glossed over a bit, in much greater detail
here.
Another factor is that apportionment is based on the National Census, which is why Trump was fighting so hard to put a citizenship question back on the Census, tried to eliminate undocumented immigrants from the census count altogether, and
did limit the number of census-takers and cancel or minimize public education programs in 2020; he knew he could encourage a deliberate undercount of certain states and thus affect apportionment. It's also why the US nearly went to war with itself over the question of how to represent slaves on the census, back when we admitted that we have slavery. The process has never been a perfect representation of the national population, and arguably was never intended to be.
