I'll elaborate on this later, but I just want to list a couple of things I desperately want for my country and city during my lifetime. For comparison, I'm also listing when other places in the world got them first. For context, I expect (hope?) to live another 50 years or so.
Universal health care, whether through extending Medicare to all residents or through some other mechanism. The UK got it in 1948, Canada in 1984, and Germany in 1883. We're the only holdout in the OECD, and it benefits no one except the owners and shareholders of private insurance companies to continue our broken system.
Universal child care, which would enable single parents to work without going broke on daycare. Much of Continental Europe makes this a no-brainer, with free day care for little kids and extended school hours for older ones. In a report covering 41 rich countries, UNICEF puts Luxembourg first, Germany 5th, Canada 22nd...and the US 40th. Only Slovakia treats its kids worse. (The UK is 35th, which is sad.)
Term limits on appellate judges, including an 18-year term for the Supreme Court and a 13-year term for the Circuit Courts. The UK and Canada require judges to retire at 75; Japan at 70; and Mexico after 15 years. Every US State (except Rhode Island) has some limitation on its supreme court, whether through mandatory retirement, term limits, or elections. This doesn't require anything more than an act of Congress, as former Justices and Appellate Judges would still continue to serve in other Federal courts "during good Behaviour." I would also like to see a Governor-appointed, single-term Illinois supreme court.
A functioning opposition party, both at the Federal level (either through the Republicans coming to their senses or a serious third party replacing them in opposition or governance), and here in Illinois. As much as I like the current Democratic trifecta in my state, I don't think single-party governance is healthy, as it tends to become single-party rule, followed shortly by something worse. All of our peer nations (except possibly the Republic of Korea) have had two or more functioning parties since the end of World War II. Only 11 US states currently have divided governments, and in 4 of the 6 most populous (California, New York, Texas, and Illinois), the party out of power has almost no power at all and no hope of getting elected this decade. Illinois farmers need an effective voice in the General Assembly; right now, they have the modern GOP.
A larger House of Representatives. We last expanded our lower house in 1913, when the US population was less than 1/3 what it is today. As of 2020, each congressional district has an average population of 762,000, with Delaware having its entire population of nearly 1 million represented by one person. The average Canadian riding has 108,000, the average UK constituency is between 56,000 (Wales) and 72,000 (England), and the Bundestag elects 598 members on a proportional basis by party and Land population. One plan I like would take the largest state that currently has 1 representative (Delaware), give it and the three smaller states 2, then use that as the size of the other districts. At roughly 500,000 per district, we'd have around 650 representatives, giving us a House the size of the UK House of Commons.
End Gerrymandering. Require that all electoral districts for any office have compact, contiguous outlines drawn by non-partisan commissions at each level of government. I would also allow multi-representative districts chosen by proportional vote (for example, a 2-person district where the first and second vote-getters win). Canada passed legislation making malapportionment much harder in the 1990s, as did the UK in 2015, while Germany has proportional representation which nearly (but not totally) obviates it. This has to be done nationally, because as the Democratic legislatures in California and Illinois would like to remind the Republican legislatures in Texas and Florida, we'll put down our guns when you put down yours.
Realistic gun regulation, including mandatory licensure and registration, limits and painful taxes on ammunition purchases, and allowing local jurisdictions to set their own regulations—up or down, for the sake of rural residents—on who can own what kinds of firearms. The UK and Australia famously enacted tough laws after mass shootings in 1996; Canada in 1977; Germany in 1973. I should also point out that Switzerland—where every adult male must own a gun—has more liberal gun laws than the US in some ways, but still restricted entire classes of weapons in 2019, and has severe penalties for misusing them.
De-militarize local police forces. There's a reason George Washington feared a standing army, and why many Americans fear they live with one today. Everyone who cares about police policy should read Radley Balko's The Rise of the Warrior Cop. All of our peer nations have strict rules against police agencies using military weapons and tactics, and most UK cops still walk around unarmed and unmolested to this day. I've used Germany as a Continental example for many of these points, so let me just say that Germany has a great deal of experience with heavily-armed local paramilitary forces, and they don't ever want to see them again. Why are we building them here? We frogs need to hop out of the pot—and soon.
Fully-electric commuter rail in Chicago. London skipped from coal to electric in the 1950s, and Munich in the 1920s. Toronto, sadly, still uses diesel trains, but they're fixing that. Sure, this would cost about $5 billion, but it would bring more than that in benefits to the whole Chicago area. For example, a side-effect of London electrifying was to drastically increase the value of workingmen's houses along rights-of-way (seriously, £1.2 m for a tiny house!), as they're awfully convenient to Central London without getting flaming cinders dropped on them anymore.
High-speed rail between most US cities less than 500 km apart, like Chicago-Detroit, San Francisco-L.A.-San Diego, and Dallas-Houston-San Antonio. (Not to mention, real high-speed rail throughout the Northeast Corridor, none of this anemic 110 km/h crap.) Most of Europe has had true HSR since the 1990s, starting with the French TGV in the 1980s. The London-Paris Eurostar came in 1994, moving people between the two cities in just over two hours—quicker than you can get from central London to your airplane seat at Heathrow. It's criminal that it takes 4½ hours to travel the 450 km between Chicago and Detroit, while you can get from Paris to Lyon (also about 450 km) in just over 2. And if they can spend £25 billion (in 2023 pounds) to build a 50-kilometer tunnel under the English Channel, we can spend half that to build a 20-kilometer tunnel under Long Island Sound, FFS.
This list isn't exhaustive, by any means. I believe the US has the resources to accomplish all of them in the next 10 years, let alone the next 50. We just lack the political will, especially in the modern Republican Party, which lacks the understanding that American greatness has always depended on collective effort.
The United States is no longer the greatest country in the world...but it could be again.