Antarctica doesn’t actually belong to any one country. The 1957 treaty separated up Antarctica between the countries which are vaguely proximate: Chile, New Zealand, Australia. No America wasn’t one of the Antarctica Treaty partners; they do however have one of the largest bases there why: because they can I suspect. The New Zealand McMurdo Antarctica base has always been a scientific, not a military base because the McMurdo area, the bases are named for the McMurdo sound are close to the famous dry valleys: the only part of Antarctica which is permanently ice free.
Logistic support in Antarctica is difficult even today :you can’t just call in a supply ship in fact the condoms in the news headlines will be on about the last supply ship to get in until the ice freezes McMurdo Bases are isolated until the spring melt in November:wintering over is probably the most isolated you can be on earth really - especially at the smaller New Zealand McMurdo Base: though I have heard that the mid-winter Christmas - celebrated on the 25 June is amazing. The only other way into McMurdo Base is by supply plane - a long flight from Christchurch, NZ.
Antarctica was what drew me to geology, my first degree. My university would send a couple of honours students down each summer to do field work. My year, in the 80’s was the first time that a female stufent went down - there was a fair bit of comment around the department at the time. Unfortunately it wasn’t me there were 2 very good students in that class and I was probably 4th or 5th - still maybe one day. Though its still not possible to go as a tourist to McMurdo
