The US delegation is being led by Senator Ed Markey. Markey chairs the Senate Foreign Relations East Asia, Pacific, and International Cybersecurity Subcommittee.

Also along are Representative John Garamendi of the congressional Nuclear Weapons and Arms Control Working Group. plus 5 other members of Congress.

Will be meeting with Taiwan's President Tsai.

A US statement:

"Especially at a time when China is raising tensions in the Taiwan Strait and the region with military exercises, Markey leading a delegation to visit Taiwan once again demonstrates the United States Congress' firm support for Taiwan"

China's embassy in Washington:

"members of the U.S. Congress should act in consistence with the U.S. government’s one-China policy" and argued the latest congressional visit "once again proves that the U.S. does not want to see stability across the Taiwan Straits and has spared no effort to stir up confrontation between the two sides and interfere in China's internal affairs."

TL;DR version:

china Taiwan us congress