It wouldn't make much sense for the US Navy to buy smaller ships.
The reason why LCS ships were relatively large, is because they were designed as ocean going vessels. Yeah, they are meant to fight in littoral waters, but on the other side of the ocean.
Coastal defense is handled by the US Coast Guard and the US Navy doesn't really face any opponent worth worrying about to need a brown water combat vessel.
So a smaller corvette, while being sensible for most Navies, is actually a waste of money for the USN.