Final answer:
The primary barrier to renewable energy use in the U.S. is the lack of affordable energy transmission systems, high upfront energy investment for infrastructure, and societal and political challenges to switching away from fossil fuels.
Step-by-step explanation:
The biggest barrier to the use of renewable energy in the United States is a lack of available and affordable ways to transmit the energy to the consumer. This challenge arises from the high upfront energy investment required to build and deploy alternative energy technologies such as solar, wind, and nuclear power. Despite the strong interest in renewable energy which originated in the 1970's oil crisis, the ongoing reliance on fossil fuels is sustained due to their efficiency and lower costs compared to renewable sources.
Renewable energies, while improving, still operate at lower efficiencies than mature fossil technologies. Together with the high upfront costs associated with transitioning to a renewable infrastructure, societal and political hurdles further complicate the move away from oil and coal. The result is an 'energy trap,' where initiating a substantial shift to renewables amid declining fossil resources could politically and economically be very challenging.
It is emphasized that to avoid the hardships of an energy trap, if society is to transition to a sustainable energy regime, it is best to begin this process while energy resources are still relatively plentiful. The long-term benefits of sustainable energy will only be achievable with the early investments in renewable infrastructure.