The only big river delta in the US is the Mississippi. East Asia has far worse problems. Most of China's port cities are on river deltas. Tapei is on a river delta. Ho Chi Min City is on a river delta. Singapore is on a river delta. These are all areas where the land to water slope is very low.

The western US is mountainous enough that there's more than enough land rise to prevent flooding more than a short distance inland. Even in places that look flat, like LA near Venice, go three blocks inland and you're tens of feet higher. Places that built on fill, such as San Francisco and Foster City, do exist, but are small enough for barriers and not fed by upstream rivers.

Other wealthier places may be able to use municipal bonds to fight sea level rise. In the valley in Foster City, the choice was between pricey flood insurance and a cheaper municipal bond to construct a robust levee and the latter was chosen. The city is small enough and the residents were wealthy enough to do it.

I'm kind of curious if anyone will attempt to damn up or construct locks under the golden gate bridge. I think the valley could be wealthy enough to do it.

Plus those grants are kinda complex to navigate, and you can't do it as an individual. It has to be part of a local communities overall flood mitigation / risk-reduction plan.

Assuming flood insurance prices are realistic (not propped up by government), eventually no new construction will happen because no one will approve/afford insurance.

Existing places will get cheaper / hell hole as rates keep going up.

Federal flood insurance has distorted market prices drastically in many places