Final answer:
The second champions of the USFL were the Philadelphia Stars in 1984, while the Green Bay Packers won the second NFL championship in 1930. The television poll for predicting NFL champions is not representative of all football fans.
Step-by-step explanation:
The question about the second champion of the United States football league touches on a historical sports topic. However, it seems there might be some confusion in the phrasing of the question, as the United States Football League (USFL) is different from the National Football League (NFL), and the mention of the Negro National League pertains to baseball, not football. To clarify, the USFL was a spring/summer professional American football league that had its last game in 1985, and the second champions of the USFL were the Philadelphia Stars in 1984. If we are talking about the NFL, then the team that won the second NFL championship was the Green Bay Packers in 1930.
It is important to note that a poll conducted by a television program does not necessarily represent all football fans. The sample is likely to be biased and not representative, as participants are self-selected viewers who decide to call in and may not reflect the broader demographics of all football fans in America.