The US needs it if they want people who are spooked my mRNA tech to get vaccinated. They also need it if they want a vaccine that is the mostly likely to be safe for use in children.
In either case, while non-mRNA vaccines may incentive the 'vaccine hesitant' to get poked, no amount of modification or scientific advance will get anti-vaxxers to get immunized edit: with a vaccine (I'm assuming an FDA-approved small molecule therapeutic would be OK with some of them).
OK, fine, it's not just mRNA. It's novel tech vs. well known tech like attenuated/inactivated virus.
Beyond that, Covaxin is the only that I'm aware of that is performing well under delta.
https://www.covid-datascience.com/post/israeli-data-how-can-...