Final answer:
President Dwight Eisenhower advised Great Britain against invading Egypt during the 1956 Suez Canal Crisis, emphasizing diplomacy and the strategic use of American military presence to prevent Soviet intervention, resulting in the United States' ascendancy as the dominant Western power in the Middle East.
Step-by-step explanation:
The US President who advised Great Britain not to invade Egypt was Dwight Eisenhower during the Suez Canal Crisis of 1956. President Eisenhower was concerned that the use of force by Britain and France in response to the nationalization of the Suez Canal by Egyptian President Gamal Abdel Nasser would increase the volatility of the crisis and potentially draw the Soviet Union into the region. He believed that diplomacy should be used to resolve the situation and depended on nuclear deterrence by scrambling US forces to prevent Soviet intervention. The crisis ultimately demonstrated that the United States had supplanted Britain and France as the preeminent Western power in the Middle East and led to the creation of the Eisenhower Doctrine, pledging US intervention against Soviet aggression in the region.