The Chinese military has started to concentrate its forces to the south-east coast as tensions between Taiwan escalate. Missile bases in the region have now begun to upgrade their capabilities, allowing for the dispatch of cutting edge DF-17 hypersonic missiles.
In addition to the weapons upgrade, the Chinese military has begun to reinforce the area with more troops. Currently 10 of the 13 PLA marine brigades are now based at the coast.
Besides the consolidation of coastal forces, China has run a series of exercises recently around Taiwan, including a large scale invasion drill.
As for the USA and its involvement, the Trump administration has put to congress its wish to sell advanced arms to Taiwan, as per the Taiwan Relations Act.