Final answer:
The Shah of Iran's move to nationalize the oil industry led to severe economic repercussions for the West, culminating in an oil crisis with escalated prices following the Iranian Revolution in 1979.
Step-by-step explanation:
The action by the Shah of Iran that had the potential to harm the West economically was his nationalization of the oil industry, which eventually led to the Iranian Revolution in 1979 and the disruption of Western oil interests. After the Shah was deposed, Ayatollah Khomeini took over and ended the oil shipments to the United States, which had been a key part of their energy strategy, and also sought to nationalize the oil industry. This shift not only severed the established economic ties but also triggered a significant increase in oil prices, contributing to the energy crisis of that period.