With the world's most powerful military, a huge economy, and a leading role in international institutions such as the UN and NATO, the USA is a superpower. The rise in power and importance of China and re-emergence of Russia will continue to challenge the global dominance of the USA.
Chinese military parade, Tiananmen Gate, Beijing, 2015
The US has also been challenged by the increasing importance of China in recent years:
although China is not a match militarily to the US, it is an economic superpower and it is expected that China's economy will be larger than the USA by around 2020
China is also using its new found wealth to increase its influence in Asia and particularly in Africa
by way of response the USA has increased aid and trade with many African countries to ensure US influence is maintained within the continent
the US is seeking more co-operation with China over the problem of North Korea pursuing nuclear weapons. The Obama administration was successful in working with partners to ensure Iran did not continue to pursue nuclear weapons
China has also entered the space race
in 2016, Beijing overtook New York as the 'billionaire capital' of the world
Donald Trump made an election campaign promise to tear up trade deals with nations that he felt took advantage of the US and helped account for its trade deficit. One of those nations was China.
Stating an unfair $500 billion trade deficit with China, in 2018 President Trump announced taxes on tariffs on Chinese goods worth over $200 billion with more tariffs threatened. In response, China has imposed trade tariffs on US goods.