Answer:
In America, the presidential election system is not through the direct vote of the citizenry, but through the indirect election carried out by the Electoral College. Thus, each voting citizen gives his cast to a specific candidate, but said will must be endorsed by the electors of his state in the Electoral College.
In this regard, each state has the number of voters equal to the number of congressmen it has in the federal Congress. Thus, for example, states like Montana or Alaska have 3 electors (since they have 2 senators and 1 representative), while California has 55.
The problem is that, to determine the electoral votes of each candidate, it has been established that whoever wins the popular votes in the state takes all the votes of the electors of that state (except in the case of Maine and Nebraska). For this reason, it may happen that a candidate in California defeats his opponent 50.1% to 49.9%, in what would be almost a technical tie, but takes 100% of the electoral votes. Thus, the right of citizens to the election of their representatives is violated, and a candidate who has not obtained the majority of the popular vote (as happened in 2016 with Donald Trump and Hillary Clinton) could win in the Electoral College.
Thus, many candidates adopt the strategy of campaigning and giving all their effort in the states with the largest number of voters such as California, Texas, Florida or New York, leaving aside other states considered less important.
Less terroristic attacks.
The Korean War. North and South Korea are still technically at war. An armistice was signed in 1953 to halt fighting, but no final treaty was signed, unlike after World War 2.
United States, NATO allies and South Korea fought against North Korea, who received aid from Chinese forces.
This an example of actual combat during the so-called Cold War between the United States and the Soviet Union between 1945-1991. The two sides had different ideologies (democracy vs. communism), which led to friction.
