Public Transportation and Smart Growth

when in your own post you write:

"Urban Streetcar lines. These actually THRIVED in the 1920s and 1930s and plans were made to EXPAND them at that time period. For example Pittsburgh’s peak year for Streetcar use was 1927, but passengers still were close to that number till after WWII. Los Angles Peak Streetcar use year was 1944. Even after WWII if urban areas had a choice AND not forced to adopt buses for political reasons (Political reasons seems to be the reason New York City started to replace its streetcars with buses in the mid 1930s) the first choice was for Streetcars. For example the City of Johnstown, the smallest city ever to use the PCC Streetcars, purchased them after WWII, for even at that date you could haul more people at lower costs with Streetcars then with the buses of the post WWII Era. Urban Streetcars did not see a substantial drop in ridership till after WWII."

Some coincidence that National City Lines/Pacific City Lines were set up during that exact period as sham "holding companies" with one purpose and one purpose only: to dismantle electric rail:

"In 1936, National City Lines, an existing bus operation which had been founded in 1920 by an E. Roy Fitzgerald and his brother[4] was re-organized into a holding company. In 1938, Pacific City Lines was formed to purchase streetcar systems in the western United States."

Both were:

"incorporated in Delaware, which does not require disclosure of any public information about directors or shareholders. It is clear that the parties involved did not want to be traced."

You're correct that it wasn't only GM, it involved Firestone Tire & Rubber in coordination with the largest oil companies of the day - making it even more of a monopoly. And it wasn't just Bradford Snell who thought so:

"Joseph Alioto, mayor of San Francisco, and also an antitrust attorney testified that 'General Motors and the automobile industry generally exhibit a kind of monopoly evil', also that GM 'has carried on a deliberate concerted action with the oil companies and tire companies...for the purpose of destroying a vital form of competition; namely, electric rapid transit.' Tom Bradley, mayor of Los Angeles testified, saying that GM, through its subsidiaries, had "scrapped" the Pacific Electric and Los Angeles streetcar systems leaving the electric train system 'totally destroyed'."

It was most certainly not "legal lobbying" - whether it was successfully prosecuted or not. GM made $billions from selling buses and was fined $5,000! God knows what kind of corruption got all of them off the hook, but anyone who doubts a significant amount of money changed hands - illegally - is just naive:

"The purpose of the Sherman Act is not to protect businesses from the working of the market; it is to protect the public from the failure of the market. The law directs itself not against conduct which is competitive, even severely so, but against conduct which unfairly tends to destroy competition itself. This focus of U.S. competition law, on protection of competition rather than competitors, is not necessarily the only possible focus or purpose of competition law. For example, it has also been said that competition law in the European Union (EU) tends to protect the competitors in the marketplace, even at the expense of market efficiencies and consumers."

http://en.wikipedia.org/wiki/Sherman_Antitrust_Act

In terms of perspective:

"There is also acknowledgment that the Great Depression, the Public Utility Holding Company Act of 1935, labor unrest, market forces, rapidly increasing traffic congestion, taxation policies that favored private vehicle ownership, urban sprawl, and general enthusiasm for the automobile played a major or possibly more significant role."

leaving the door open to a conclusion that illegal antitrust actions by the largest corporations in existence could possibly be the main reason for the disappearance of American urban light rail. That is the "proper level" of significance for these truly heinous crimes and your paper should acknowledge it.