How far out into the ocean is the US border?

Answer 1

tho there are a few relatively minor exceptions the us borders with Mexico & Canada extend generally about 12 nautical miles

or about 14 statute miles

out into the seas from the coasts

as do the outer limits of all the territorial seas of the united states that are projected from all its coasts including islands

the us borders with Russia & the United Kingdom however

tho they also extend seaward up to 12 nautical miles

are in most places much closer to the coasts than this because they split the difference between islands that are sometimes only a few miles apart

so in a nutshell

the us border can be anywhere from zero up to about 14 miles out into the sea

& it is probably preferable to say sea rather than ocean because some of the seas are not really oceans but only gulfs or bays or passages etc