How many miles out into the ocean does the US own

Maritime boundaries are divided into three seperate zones - the territorial zone, the contiguous zone and the exclusive economic zone

For the US:
Territorial zone - 12 nautical miles (approx. 22.2km)
Contiguous zone - 24 nautical miles (approx 44.4km)
Exclusive economic zone - 200 nautical miles (approx. 370km)

So the US extends to a maximum of 200 nautical miles out to sea