The original point of having districts was because states are "too large" and you want people representing an even smaller geographical area so that truly local issues are represented.
And in many places that's still the case, and is actually useful and important to get local issues surfaced properly.
For states with heavily gerrymandered districts, though, I agree: might as well just do away with districts and have the entire state vote for their entire roster of representatives.
So instead of making a choice between 2-5 candidates (major 2 plus a few independents/smaller parties), every voter has to rank up to 50 candidates (assuming ranked choice voting)? How do you expect voters to know the policy positions of that many candidates? They may as well be picking at random.
If not ranked choice voting, how would this even work?
If you're going to have a large multi-member district with proportional representation, it's not essential to use ranked-choice voting - you can get a reasonable result just by having people vote once for the ticket of candidates they prefer, then allocating the seats proportionally.
That said, ranked-choice voting in large multi-member districts is certainly possible: It is usual to require voters to rank only as many candidates as there are vacancies, though they can number more if they wish to (consequently they don't need to understand the detailed policy positions of the minor candidates that have no realistic chance of election). Voters in such systems tend to firstly order the parties based on the policy positions of those parties, then order the candidates within those parties if they have a strong opinion of the relative merits of those candidates.
I'm not sure what you're suggesting. Individual districts are going to have problems the the rest of the state or country don't know/care about. Having a representative for these districts makes sense.
For example, in my district (Brownsville in Brooklyn), we have an almost tragically poorly-ranked school system, due largely to bad funding and high crime rates in the area. I don't expect someone from Midtown Manhattan to care a whole lot about these specific problems (I know I certainly didn't when I lived in Washington Heights).
In an ideal world I guess I'd agree, everyone would care about everything at the exact appropriate weight, but that's not the world we live in. Certain problems will go ignored if we don't have fairly-granular representation for an area.
That's not a great example because really the school budget should be set at the state level and distributed evenly to every district based on student headcount.
You do make a valid point that many issues are local and that could be lost in a system where the party is focused at the state level instead of the local level. Proportional representation systems are prone to having this issue for example.
Some areas are going to require more funding than others. For example, certain areas are wealthier and as a result are less reliant on the after-school programs, while poorer areas have a higher likelihood to be single-parent, or both parents having to work, meaning that the after-school programs are vital.
That's just one example, but it's not as simple as "give a certain amount of money per kid to the schools", and saying this is reductionist.
I think America really likes them because the alternative seems like "virtual representation" (i.e. representatives represent everyone, not a local district), which was part of why they rebelled against England. The theory is you want someone to represent your local area specifically rather than all representatives trying (badly) to balance the needs of everyone.
I don't know what the difference would really be in practice, although I think the other comments in this thread about lack of proportional representation would probably apply. I think it sort of comes down to how much worse you think Tyranny of the Majority is than what we have currently (or if you want an actual proportional representation system instead).
Because otherwise every voter would need to cast a vote on every single candidate for every single seat in the legislature. It's impossible to make informed choices with so many options.