The attack of the Marine Barracks in Beirut forever changed global perspectives on terrorism because it unofficially marked a policy of hostility by many in the Middle East towards presence of American peacekeepers, and it marked a strong dissent of western countries toward Middle Eastern terrorism.
After the end of World War Two and the creation of Isreal, conflict in the region was a series of domino effects; many Palestinians were angered at the creation of the Isreali state, and the surrounding Arab countries supported efforts to maintain Palestinian presence and oppose Jewish presence. Lebanon, which borders Isreal to the south, shares much of the cultural heritage with the Palestinians, and they wished to support the war efforts. However, the Lebanese also feared the power of Isreal, and they could not afford to go to war with them. Many in the government were forced to walk a fine line, and they often turned a blind eye to guerilla groups.
Initially, US troops were sent as neutral peacekeeping forces. They were generally accepted and welcomed in the region. However, as the US began to increase its support for Isreal, many people began to feel isolated and that the US support of Isreal undermined any peacekeeping efforts it sought to perform. Additionally, Middle Eastern politics were made messy by US involvement in support of the Iranian Shah and his brutal SAVAK. Many of the men that signed up for these efforts did so eagerly to help maintain peace, and they paid the ultimate price when the US violated their neutrality. 241 American servicemen and 58 French soldiers died when a truck carrying 10 tons of nitroglycerin crashed into a US Marine base.
This led to a retaliation by the US for these attacks, and it further escalated tensions in the region. Despite dissent from the Pentagon and top military officials, the US continued to support Isreali efforts, and this left a bad taste in the mouth at home and abroad. Many Palestinians and Arab countries continue to resent American presence because of a lack of neutrality, and Americans resented people of Middle Eastern descent because these Marines were attacked. Because of this bitterness and a perceived lack of stability (without a knowledge of many historical US policies), many are quick to equate Arab-Americans with the actions of a few, which further escalates the cycle. In this way, the attack of the Marine Barracks in Beirut set a policy of hostility toward Americans by Arab countries and hostility toward Arab countries by Americans that continues to influence politics and global culture to this day.