I'm not even talking about abolishing ICEs or anything like that. I'm just talking about fixing whatever political problems cause America to take literally decades to build a single bridge or other infrastructure, when other industrialized nations get it done in a small fraction of the time and cost.

You're cherry-picking counter-examples. No developed country, overall, has the infrastructural problems that America has. America just canceled its high-speed rail in California, yet Japan is already working on a maglev train scheduled for completion in 2027, and China already has one between Beijing and Shanghai. Japan's Shinkansen has been operating since the 1960s, has had zero accidents in all that time, and has an average delay of less than a minute. Germany and France also have very impressive high-speed train systems. Meanwhile, all the US has is the Acela, which is a joke.

You only mentioned airports in your examples. America can't even build rail lines that go to airports!