*Jim said, Play Nice.
The US data comes from the CDC and state health agencies. Data for other countries comes from a variety of sources.
Info on Worldometers, from the "about" link at the bottom of the web page:
"About
"Worldometer is run by an international team of developers, researchers, and volunteers with the goal of making world statistics available in a thought-provoking and time relevant format to a wide audience around the world. It is published by a small and independent digital media company based in the United States. We have no political, governmental, or corporate affiliation. Furthermore, we have no investors, donors, grants, or backers of any type. We are completely independent and self-financed through automated programmatic advertising sold in real time on multiple ad exchanges."
I recall that someone on this forum tried to discredit Worldometer by claiming that it is a Chicom website. However, given that the Chicoms initially tried to hide the Covid-19 outbreak, that makes no sense. China would want to downplay the number of cases to save face, since it was their early effort to deny that there was an outbreak that led to Covid-19 becoming a pandemic. If China would have been upfront and honest at the beginning, it is likely that the outbreak would have been contained to its original location.
Click on USA under worldometer/covid-19 data. Look under each state and go to source and click on (1) and you will see that data comes from each state’s health department.