Final answer:
The foreign policy challenge the student is asking about is linked to the issue of nuclear proliferation, which includes efforts to prevent the spread of nuclear weapons and ensure nuclear materials are secured from non-state actors.
Step-by-step explanation:
The major foreign policy challenge associated with the threat of dangerous governments or radical extremist groups obtaining access to atomic weapons is linked to the issue of nuclear proliferation and the stabilization of nuclear material. Dealing with the proliferation of nuclear weapons, a primary concern of U.S. foreign policy, is a global security problem that involves preventing the spread of nuclear weapons and technology, ensuring that nuclear materials do not fall into the hands of non-state actors such as terrorist groups, and managing the diplomatic challenges brought forth by the ambitions of nations like Iran and North Korea who seek to develop or have developed nuclear capabilities. Historical treaties such as START and the Nuclear Non-Proliferation Treaty demonstrate ongoing international efforts to address these challenges.