Taiwan
The United States’ relationship with Taiwan is a longstanding one and one that is being threatened by China’s current actions in the region.
China and Taiwan split during a civil war in the region decades ago and now Communist China is looking to secure what they believe is rightfully theirs, that being the region of Taiwan. This is a conflict that has been brewing for a long time and the US will likely get involved if things get serious.
The US has had a long-standing relationship with Taiwan and this recent incursion by the Chinese government is something the US will likely respond to.