Big picture, you'd have to say things have gone very well for the US since its founding. From a few million people clinging to the East Coast, praying that Britain and France remained occupied with each other to continent-spanning hyperpower, that's about as good a couple of centuries as a country's going to have, geopolitically.
Much credit, frequently bordering on hagiography, is generally given to the revolutionary generation, for winning independence, then framing a sturdy constitution. But there have been some glaring missteps here and there. Mostly little things--I'm not talking about slavery here, which was basically baked in to the early USA and wasn't going anywhere without eventual bloodshed. Some notable screwups:
1. Electing the President and Vice President. That was just a mess in the Constitution. It relied on electors managing to conspire to give one vote less to the desired VP. That worked sort of OK for the two Washington-Adams coronations, but was a serious trainwreck in the next two elections. In 1796, Jefferson ended up VP to his bitter opponent Adams. 1800 was even worse, with Alexander Hamilton working against Adams for the more reliable Federalist Charles Cotesworth Pinckney, and a miscommunication leading to a tie between Jefferson and Burr, despite everyone knowing that Burr was supposed to be the VP. Multiple rounds of voting in the House failed to resolve the issue, with the Federalists supporting Burr to deny Jefferson, their bitter enemy, the presidency. Finally Hamilton signaled support for Jefferson as the less dangerous man, and the vote went to Jefferson in the 36th ballot.
Soon thereafter the 12th amendment was passed, clearing the situation up by making the electors cast specific votes for President and VP. That explicitly prevented the 1800 scenario from occurring again, and effectively prevented the 1796 scenario (President and VP being opponents). However...
2. It still left the vice presidency vacant if the VP ascended to the presidency. Which turned out to be a common enough occurrence--John Tyler, Millard Fillmore, Andrew Johnson, Chester Arthur, Theodore Roosevelt, Calvin Coolidge, Harry Truman, and Lyndon Johnson were all to serve without a VP (until/unless they were re-elected in a later election with a new running mate). Only in 1967 did this finally get resolved with the ratification of the 25th amendment, allowing the nomination of a VP by the president, to be approved by Congress. Within a few years this was useful twice. First when Spiro Agnew resigned for being the 97th most corrupt member of the Nixon Administration, to be replaced by Gerald Ford. Second when Nixon resigned, Ford replaced him, and then nominated Nelson Rockefeller to replace himself as VP.
Overall, you've got to give the framers a little crap for not foreseeing any of these issues.
3. The House of Representatives is supposed to be volatile, with lots of turnover every two years in response to changing public opinion. Instead with gerrymandering, safe districts, and fundraising advantages, incumbents tend to be very difficult to defeat. House turnover is generally rather low (though this year is probably going to show a big move).
4. Political parties--the founders totally missed out on them. The system they designed is almost guaranteed to produce two strong parties, but they Madison, Hamilton et al. were all idealistic about how legislators would decide each issue on its merits, then fall back into neutrality. By 1796 the Federalists and Democratic-Republicans were all but official. With minor interruptions (the Federalists faded, leaving the D-R's alone on the field for awhile, until they split into the Whigs and Democrats, then the Whigs faded to be sort of replaced by the Republicans) we have had two strong parties ever since.
5. States. The first thirteen were existing entities in 1787, so it's entirely understandable that they were admitted intact despite their disparate sizes. But as the continent was conquered and purchased, the new states should have been more judiciously drawn. Most egregious was the decision to make California a single state, which now has about one ninth of the entire US population, yet as many senators as Wyoming. California has sixty times as many people as Wyoming. That is ridiculous. Also, did we really need a North and a South Dakota? That's a lot of senators to hand to fairly empty farmland. Surely one Dakota would have been OK.
6. Federalism. The idea was that local government is closest to you, state government next, federal government the farthest away. Closer would mean more responsive. But really, doesn't it seem like moxg people don't even know the names of their city council and state representatives? Everyone knows who's president, most people know who their senators are, same for governor. How responsive can local government be if 85% of the voters don't even know who they are? I don't have the slightest idea what my city is doing most of the time. State government has seemed inept and corrupt every place I've ever lived.
