Modern transportation has made campaigning much easier. A presidential candidate can now crisscross the country and visit every important state multiple times. In the early 20th century they used trains and whistle stop tours, going to all of the small towns on weeks long tours.
This is a very esoteric question, not one that is usually discussed in US History classes. I would therefore imagine that your teacher or book has said some things that you are expected to remember. Please check.
That said, if I had to answer this I would say that transportation improvements over the past 150 years have made the political climate in America more democratic and participatory than it once was.
150 years ago the boom of railroads was just starting. From then on, travel around the country has become easier and easier. Because of this, politicians have been able to see more of the people who vote for them (and be seen by those people). This has helped to make people feel more as if they have a stake in government and it makes them feel more as if they are in contact with their leaders.
As people came to feel this way, they started wanting more and more input into the governmental system. That is one reason why we now have things like primary elections and senators elected by the people -- things that let the people have more say in government.
Developments in transportation has made transportation of people as well as goods faster, and more economical. This has led to every place in the world more connected to all the other places. Each place in the world is effected much more by the rest of the world, and in turn each place is able to exert much greater influence on rest of the world.
Net effect of this is that it has increased the level of interdependence between people of different places. There is much greater economic and political interdependence between regions within countries and between different countries. One good example of this interdependence is the worldwide recession that we are currently passing through.
Speaking specifically of impact on politically climate, we see that people of any place are much more aware of different political concepts and development from different part of the world. This makes people much more politically aware. Also people give much more importance to national and international issues as compared ti just the local issues. The politicians also have realized such changes in general population and have changed their political approaches and strategies accordingly.