US law no longer requires a copyright notice since March 1, 1989.
However note that while copyright notice are not required in US law, they are still recognised by US law, and it is beneficial to add them. If someone removes the optional copyright notice, they are committing an additional federal crime of concealing the infringement.
Good Open source licenses are written to be enforceable in jurisdictions worldwide, and written so they trigger many parts of the law to offer maximum protection.
https://en.wikipedia.org/wiki/Copyright_notice#Reasons_to_include_an_optional_copyright_notice for more details.
Many licenses allow the implementer to include a custom bit of text. Sometimes it is called the advertising notice, or attribution notice. For Apache 2.0, special consideration is given to a file called "NOTICE", which is where you would put the following text to ensure that it can not be removed.
Project is open-source and made by the following contributors: *github list of contributors link*
Finally, while not mandatory, it is Apache-2.0 best-practise to add a short "header" to every source file in the project so there can be no doubt the Apache license applies to that file. See https://www.apache.org/licenses/LICENSE-2.0#apply