Indeed you are right. Over the kind of commute distances in the USA, and given the vast urban, suburban and semi-rural sprawl that characterises large parts of the US, it's very true. Mass transportation doesn't work in large parts of the USA, due to the low densities of housing. Unless you count Aircraft. Which seem to work fine as a mass transit system (see later!)
High speed rail (and by high speed I mean anything that goes at 100mph+) can help with shrinking the sprawl effect though. If you do high speed right, you can co-ordinate express commuter and long distance high-speed trains. The Japanese do it on the Shinkansen. The British on their High Speed routes. The Germans... need I go on.
I used to commute about 20 miles (in each direction) every day, from a commuter village near a small city to a business park in a much larger city. That involved a 10 minute bus ride, followed by a 12 minute train ride, followed by a 5 minute metro ride, followed by a 10 minute walk. That journey took an hour, including all changes, door-to-door. In rush-hour traffic, you're talking about 50 minutes drive. So, despite all those changes - what kept the journey time down? Spending those 12 minutes on the train at (or near) 100mph. It meant I could do 16 of those miles in 12 minutes. I tried going the whole way on the (more frequent) bus. Add 30 minutes.
So High Speed rail can help in the daily commute. In the UK, daily commuters to London come from as far away as Yorkshire (170-200 miles). They can do the bulk of their commute in 1hr 45 minutes.
The big trick with commuting using high-speed rail is plumbing the high-speed rail system into the cities' mass transit systems at either end. By doing this you can start to make longer-distance commutes effective by public transport. Most European cities have their subway, light rail and bus networks closely tied into the intercity train system, usually sharing station sites. That makes a difference. Even just making the nearby city bus routes stop at the front of the station can make a huge difference to this. That's where I think agencies like RTD in Denver have the right idea - bring the trains and the buses into the same place.
The other important thing is that the FRA (Federal Railroad Administration) need to get their heads out of their backsides and quit imposing utterly ridiculous crashworthiness standards on the trains. On a high-speed rail system you put the crashworthiness (or lackofcrash-worthiness) into the infrastructure itself, not the trains. That's what the entire rest of the world does. It means you can use light, efficient train sets, allowing the commuter trains to accelerate all the way to 100mph+ at the same rate as a light rail vehicle. It also reduces the maintenance required to the route, making both the trains and tracks cheaper to run, because of the reduced axle-loadings and lower energy costs. The imposition of a "Positive Train Control" system over the entire existing intercity networks will go a long way to preventing crashes, and once it is implemented, the FRA really need to reconsider their approach.
To be honest, any approach to high speed rail would likely take 20-30 years to truly bed-in. "Transit oriented development" needs to be more than a buzzword - it needs to become second nature - for a true change to work. That means people need to get in the habit of thinking "I will buy this house because it is near a good bus route" or "This house is only 10 minutes walk from the station" in the same way that people currently think of "only 5 minutes from the interstate". That's when the big changes will start. But to get there, you need to reduce the barriers to using transit, and consider raising the barriers for running a car. High Speed Rail can form a part of that.
The final question is what is being competed against? In most of the developed world, the high-speed train networks are often geared around being competitive with airlines on journeys in the 100 - 400 mile area. If you site your stations well, and use existing rights-of-way to access the downtown area, coupled with a close tie-in to city transit, higher speed intercity rail can compete very well with regional jets, and routinely does. There's no point building high-speed rail for the coast-to-coast journeys - build them for regional intercity and commuter travel, the way Obama is pushing now. He just needs to get the cities to connect their buses to his new stations!