During the presidential campaign, Donald Trump's strong rhetoric on South Korea and Japan playing an enhanced role in their own defence, as well as their ability to move forward with their nuclear weapons program, created some cause for concern within those states and the region.
The statements portrayed an image of US regional "retrenchment" , but recent events—such as the testing of ballistic missiles by North Korea—have altered the situation. Indeed, under the new administration, US presence in the region has increased, specifically with the deployment of the Terminal High Altitude Area Defense (THAAD) which is directed towards the defence of Seoul against Pyongyang.
The US has proven through its actions a willingness to not only continue but to strengthen its position in the region, especially through its alliances there.
During the campaign, Trump's statements on Tokyo and Seoul becoming nuclear powers also seem to have not been worth their weight in the worry they caused. Clearly, President Trump is beginning to take a different line than candidate Trump.
Though the idea of regional countries playing a greater role might have garnered support within certain sections in Japan and South Korea's leadership, the US certainly would not strategically approve of it as it would threaten American hegemony in the region. The US has proven through its actions a willingness to not only continue but to strengthen its position in the region, especially through its alliances there.
Throughout the campaign questions were raised as to the future of the US presence in the Asia-Pacific. This was especially true when Trump with the stroke of a pen pulled out of the Trans-Pacific Partnership (TPP). Since then, administration has effectively answered those lingering questions with the deployment of THAAD. In fact, his campaign rhetoric regarding Seoul being a nuclear power, should be taken as a clear sign of the US creating further inroads in the region.
The US presence in the region is in fact going to increase given the behaviour of China and North Korea. Though the allies (Beijing and Pyongyang) seem at logger heads especially over the missile test, the situation could change in the blink of an eye when the US is thrown into the mix. On the other hand, China's posturing continues to increase, especially in the South China Sea and the Sea of Japan—perturbing many countries in the region including the US. Washington's military foothold in the Asia-Pacific as a result of its alliances, gives it unprecedented opportunity to play a greater balancing role in the region. Therefore, the continuous US presence in the region has become essential for the allies as well as for the future of US regional power. However the deployment of THAAD has irked the Chinese as they see it as a threat to their military capabilities. The system is already in Guam, thus upping the strategic security ante. A reaction from China could be in the form of an indirect counteractive strike at Japan, South Korea or Taiwan.
Now the bigger question is not so much about abandonment but rather "tipping the scale" in the opposite direction.
Pyongyang's increasing unpredictability is also clear, especially given the recent missile tests that were aimed at examining the US response. Now its rhetoric has extended to the threat of "nuclear war". Washington responded in equal measure by putting the option of "military" more firmly on the table.
Trump has already signalled that the US will support its allies and oppose an adversary. This has been a drastic change since the campaign, a sort of maintaining the status quo. However, now the bigger question is not so much about abandonment but rather "tipping the scale" in the opposite direction. The regional allies are beginning to wonder whether Trump has gone to the other extreme.
The temperatures are certainly running high in the region. The uncertainty over whether Trump's presidency is moving away from or moving towards the Asia-Pacific region has certainly sparked a great deal of concern for all parties involved.