One thing I love about alternate history is that it can be a mental exercise which broadens your horizon. You realise which things depend on which other things, so what you took for granted and considered as a natural background feature is actually dependent on political decisions, on evolving cultural concepts, on technological innovations, on economic shenanigans etc. all of which could have gone in many different ways.
Thus, when in threads like this (and there have been many on the topic of railroad vs. auto transportation lately) some people state that the US is simply too vast and thinly populated, cars are simply too convenient, subsidies are something that concerns only trams and trains etc., I feel that this potential of alternate history is not tapped. It's a bit like the geographical determinism I've encountered in the Pre 1900 section when people claim that an industrial revolution is bound to begin in Britain in 9 out of 10 cases because of treasures of the soil, maritime commerce and the like. This is not to say that geography or other un-historical factors are completely unimportant. They are important, and US mobility is therefore always bound to look differently than Singapore mobility, just like Swiss mobility is looking differently from Danish mobility. But are we really freeing our minds enough here?
I believe many people are right when they say that a PoD has to be rather earlier than later. As always in AH, we must not underestimate how much the world is changed by a PoD in, say, the early 20th century. A different WW1 almost certainly butterflies the New Deal and Hitler's Autobahnen, and it absolutely certainly butterflies Eisenhower's interstates.
There clearly is a connection between (sub)urban geography, communal political planning, culture, and modes of traffic. Suburbia has been viewed in many different ways by different people across time, just like inner cities have; IOTL it has ingrained itself so deeply into culture that it may be difficult for us to disentangle ourselves, but I doubt that even if we assume capitalism as the dominant economic system of the 20th century and technological developments not being majorly hindered, OTL's mix of suburbian sprawl, universal automobility, road privileges, car culture, tram and train deemphasis etc. are something towards which US development naturally gravitates in any TL. (Actually one of the reasons these threads might pop up so often now could be that, for a few decades, inner cities have become hip now and expensive and places where wealthy and well-educated people live (, too), so this cultural change is probably mirrored here. Just like in the opposite earlier case I've argued for, here, too, we're not talking about an inevitable development, either...)
To return to some degree of concreteness, I'll just play with the WW1 PoD proposed in this thread: no US involvement.
It could - but does not need to, of course - produce the following consequences: Russian Provisional Government sees the futility of staying in the war and concludes separate peace, no October Revolution, no Soviet Union, no elimination of Ukrainian grain from world market, less of an agricultural spike elsewhere in the 1920s; WW1 ends in stalemate, no British hegemony in Arabia, less cheap oil in the West; central Europe more politically and economically stable, no Weimar instability, no Hitler, no Autobahnen, no WW2, no Eisenhower; probably no progress enthusiasm of the "Roaring Twenties", socio-cultural patterns including self-concepts of the middle classes resembling to a greater degree those developing pre-WW1; no cultural etc. exodus from Berlin, Vienna etc., US looks e.g. to EUrope for cultural inspiration at least as much as the other way round (virtualy everything upon which, say, "Rebels Without a Cause" was based, is removed by now)... You can take it from here. Or you could take tons of other routes, where, just like always in alternate history, small changes will produce great divergences. Of course, the above scenario could also produce different consequences, in which US infrastructure resembles OTL more closely. But it doesn't have to. It's not ingrained in a "US mentality", nor is it determined by the natural geography of North America or anything else beyond human control.
