I know that the orginal fort in St. Augustine was Spanish, but unless I'm mistaken, isn't the current iteration the one that was built in the 1820's? Fort Mark or Marion or something "M"y I think. . .
The Spanish had a grand time calling every little settlement a "fort" and building plans for them. I've done a lot of digging at a site that had grand plans for forts. . .the reality was likely something a little (lot) less grand that rotted away.
The forts we all like to visit are mostly American and 1800'sish, I think, even if there was an earlier fort on the location. The Americans built in stone and brick and there hasn't been any regime change since those forts were built, sooooo. . .
But, again, I don't do much in military history. Just enough to get me by. . .