A general rule of thumb is that you lose 100 feet of coast for every 1 foot of sea level rise. Island nations will feel it first.

Miami and much of southern Florida is already fighting salt water incursion, though it is mainly due to groundwater removal. This will get worse over time with a rising sea. Also, much of that area is barely a meter above sea level. By the end of the century, Miami might be the northernmost of Florida's keys.