If you have filed a 2019 tax return and need to change or add your direct deposit information, see this IRS website - https://www.irs.gov/newsroom/economic-impact-payments-what-you-need-to-know
In the coming weeks, Treasury plans to develop a web-based portal for individuals to provide their banking information to the IRS online, so that individuals can receive payments immediately as opposed to checks in the mail.
Regarding the American Rescue Plan-
“This has not yet become law.”
https://blog.turbotax.intuit.com/tax-news/american-rescue-plan-what-does-it-mean-for-you-and-a-third...
If it becomes law, after signed by the President, then the IRS will have to go into the IRC to make changes and then update their systems and then put the information out to software developers, who will in turn have to make changes to their software which may require IRS approval.
We will have to wait and see what happens to determine what, if any, new course of action should be taken by taxpayers.
