As of today, Apple, Alphabet, Meta, Amazon, Microsoft and ByteDance, the six gatekeepers designated by the Commission in September 2023, have to fully comply with all obligations in the Digital Markets Act (DMA).
The DMA aims to make digital markets in the EU more contestable and fairer. It establishes new rules for 10 defined core platform services, such as search engines, online marketplaces, app stores, online advertising and messaging, and gives new rights to European businesses and end-users.
Just happen to be that big tech is located in USA.