Again - America has been a thing since 1776.
Australia since 1901.
How has this not been sorted yet?
Are any Americans on this list able to devote an hour a week to setting up an online campaign to get this thing rolling? To generate a conversation around Constitutional reform?
Constitutional amendment is an incredibly difficult process (I think it's the hardest constitution to amend in the world? I could be wrong) to the point that people, perhaps not wrongly, generally just have to sigh and shrug at the idea and try to seek results elsewhere. The US constitution being so astoundingly difficult to amend certainly made some sense back in the late 18th century when states had a fear of signing up for the Constitution only for the other states to pass a bunch of amendments stripping away their sovereignty, so a very difficult to amend Constitution was a strong guard against that (it was actually easier to amend the Constitution than the original Articles of Confederation, which required unanimous agreement for any amendments). Nowadays, unfortunately, it means that problems with the Constitution must go unfixed because of the difficulty in fixing them.
That said, strictly speaking, no constitutional reform is needed, at least for the federal House of Representatives. The Constitution says:
"The Times, Places and Manner of holding Elections for Senators and Representatives, shall be prescribed in each State by the Legislature thereof; but the Congress may at any time by Law make or alter such Regulations, except as to the Places of chusing Senators."
So things like districting are normally left up to the states, but the federal government can override those and set up its own fairer districts if it wants, or even abolish districts and set up proportional representation (they would probably need to expand the House's size to do this effectively, but the House needs an expansion in size regardless). So the federal government could end gerrymandering for the House of Representatives (it has no power over gerrymandering for state legislature races, though).
Then again, it could also do the opposite and make gerrymandering far worse, and all in one direction rather than a mixture of Democratic-gerrymandered and Republican-gerrymandered states. If one party captures the trifecta of president/house/senate and is daring enough to abolish the filibuster, it seems to me they could absolutely gerrymander
every state in their favor to likely give themselves perpetual control of the House of Representatives.