Territorial disputes in the South China Sea have always existed. It is full of fish, and important trade routes run through it. But the aggravation is primarily due to the fact that on the shelf of the sea are huge reserves of oil and gas. According to the US Department of Energy, there are oil reserves up to 5.4 billion barrels and gas to 55.1 trillion cubic meters. And for the sake of owning these natural riches, the states of the region are ready for much.
The US position is that they are trying to act as a mediator in resolving the conflict, calling for respect for the freedom of naval navigation in the South China Sea and supporting the interests of the countries parties to the dispute with China.
The US is using territorial disagreements between China and other countries in South-East Asia on the use of the South China Sea to consolidate own interests in the region. The fact is that the water area of the South China Sea is important for the US naval communications. Also, the South China Sea is an "outlet" to the markets of the South-East Asia countries, trade turnover with which constitutes a significant share in the US budget. Moreover, navigable routes pass through the South China Sea, which are used to transport hydrocarbons to the United States from the Middle East.
The US acts as a defender of the interests of small countries against the hegemonic policy of Beijing and as a defender of the principle of the free sea. At the same time, it is strange that the US calls on China and other countries to comply with the international law of the UN Convention on the Law of the Sea of 1982, which US have not ratified. In general, the US strengthens position in the region protecting the freedom of navigation in the South China Sea, the interests and rights of individual participants in a territorial dispute, for example, Vietnam or the Philippines. However, Beijing expresses the unacceptability of the internationalization of the South China Sea issue and the intervention of a third party, since the US is not a party involved in a territorial dispute in the South China Sea.
The US is now masterfully managing foreign territorial disputes in the South China Sea, with little or no risk. It in fact do not recognize the sovereignty over these archipelagos behind other participants of territorial dispute. The US simply oppose the sovereignty of China, but that's enough that some countries in South-East Asia support the strengthening of the US military presence in the region. At the same time, the image of the US as a friend and defender is steadily created, but China as an enemy and aggressor, while Washington's political influence is growing against this background. If necessary, the US can sacrifice some regional pawn, if the geopolitical game becomes aggravated.