It's mostly river deltas that have this problem. A small sea level rise reduces flow at the river outlet, causing flooding out of proportion to the sea level rise.

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.