Decolonization played something of a role in the creation of the State of Israel because it helped bring about the conflict that surrounded that creation. After World War II, many of the Arab states of the Middle East gained their independence. This happened as the UK and France lost their overseas empires. As this happened, Arab nationalism gained force. Arabs came to feel more empowered by the new-found independence of many of their brethren.
One place that did not gain independence was Palestine. The UK was given a League of Nations mandate over the area after WWI. During the time of the Mandate, the UK had a hard time deciding who should eventually own this land. Beginning with the Balfour Declaration, the UK seemed to favor creating a Jewish national state in the region. Other countries of the West, notably the US, supported this idea after the horrors of the Holocaust. This led to the creation of Israel.
However, Arabs who lived in Palestine did not want a Jewish state on what they regarded as their own territory. Their nationalist feelings, combined with religious differences, made them unwilling to accept the new Jewish state. This led to war between various Arab states and the new country of Israel.
Thus, we can say that decolonization helped to create Arab nationalism. The process of decolonization and the rise of Arab nationalism (along with the West’s unilateral decision to give Arab land to a new Jewish state) made peace impossible in the region.