[gpm]

Hmm, no I don't think Georgia or South Carolina are too far north, I'd be more worried that their coasts look pretty populated - and generally I'd expect that to be doubly the case around river mouths.

To put some numbers on the "north"ness.

Boca chica is at 26 degrees north, which gives you 416 m/s free velocity (1500 km/h) [1]. The southernmost point of Georgia's coast is at 30 degrees or 401 m/s, the southernmost point of South Carolina's coast is at 32 degrees or 393 m/s.

Actually calculating payload to orbit is more work that I don't really want to do, but you can find someone else who put in the work on this stack overflow question [2], just for different latitudes and a different rocket. 28 to 30 degrees is roughly a .3% change in payload capacity in their model.

You're definitely not the first to suggest Peurto Rico, but I think you have the same problem of there not being enough empty land [3].

[1] https://www.google.com/search?q=%28%282+*+pi+*+6378.14+km+%2...

[2] https://space.stackexchange.com/questions/998/how-much-of-an...

[3] https://www.quora.com/Why-don-t-we-build-a-rocket-launch-sit...