Well, if you’re arguing the intended effect was to do a poor job at producing the proper effect, I think that’s a somewhat different argument. No government in the late 18th or early to mid 19th century intended to ultimately provide universal healthcare or access to education. Nor did they envision the need for anything like modern infrastructure. So I think reaching back two centuries to make the case that the US government is functioning as intended is a bit of a stretch.
I concede America’s history of slavery and racism plays a role in its domestic troubles as well. From a constitutional perspective the federal government had the tools to deal with this far more effectively after the passage of the 13th, 14th & 15th Amendments. Therefore, I would argue that to the extent the federal government was ineffectual at dealing with its racial problems— at the very least until the passage of the Civil Rights and Voting Rights Acts — it was for cultural reasons. Indeed, I would argue the current gridlock & rise of Trumpism are cultural phenomenon largely unrelated to any constitutional issues the founders burdened us with.
That said, my argument regarding ineffectiveness was intended more as a challenge to the situation developing over the past three to four decades rather than over the long stretch of US history. That the federal government was able to rise to the occasion during the Great Depression and through efforts like the Marshall Plan in the post-war years only serve to demonstrate it can be effective when it has to be or feels it is in its interest to do so. The American people have lost faith in their capacity to do great things like that and their leaders have encouraged this lack of faith. That’s the problem.
We have seen the US government becoming progressively less effective over the course of most of my lifetime. This ball really got rolling around the Vietnam and Watergate eras (both admitted failures of leadership) and was slowly but more or less steadily accelerating until recently. Now it appears to be accelerating quite rapidly. In large part this is due to the fact that we have one major party whose platform since about 1980 has been built upon the premise that government, at least at the federal level, can’t work effectively — as opposed to doesn’t work effectively. When you start from that premise and your party is running the government, it’s practically inevitable that government will fail to function at anything close to peak efficiency/effectiveness.
I agree that geography plays a role, though most especially in the case of the United States. It’s been blessed with two major oceans on either side that have protected it from invasion throughout its history (the War of 1812 notwithstanding), along with both weaker and relatively friendly nations to both its north and south. It’s rise as a superpower likely would not have gone nearly so smoothly had it not been for this fact. If we’re taking the long view, Europe has historically been cursed with far more violence and disruption than the US, even if we take the Civil War into account. With regard to Japan’s historic xenophobia and intolerance for immigrants, its population is currently declining. As for latitude correlating with relative wealth and good governance, we need to be careful not to draw any conclusions about proximity to the equator being the primary cause. It’s also been the case that nations in the global south were conquered by the European powers and spent at least two or three centuries as their respective colonies as a result. There were, of course, other variables — almost too many to mention. Jared Diamond and others have done a reasonably good job of documenting these.