Over in The Atlantic, David Litt argues that Congress should be much larger than it currently is:
In the 90 years since the cap [on the number of reps in Congress] was put in place, the number of House seats has stayed flat while the population has boomed. To put it slightly differently, each member of Congress has become responsible for several times more constituents. District populations have doubled since my parents were born, in the late 1950s. In my own 33-year lifetime, the number of Americans per lawmaker has increased by about 200,000—the equivalent of adding a Salt Lake City to every district in the United States.
Believe it or not, I've been working on a similar post, coming at the argument through looking at the ratio of people-to-reps in other countries.
Litt makes the case much better than I ever could (for example, I didn't know that the number of House Reps was commonly increased after every census until 1919!), but here's a plot of person-per-rep vs population for about two dozen democracies, from Mexico to South Korea to Nigeria to Norway:
You'll notice most countries are clustered together in the lower-left-hand corner.
See that outlier, waaaay up in the corner, far away from everyone else? That's the United States.