sport importance

Are sports important for getting into uscga? My parents wanted me to stop doing club volleyball and focus more on studying for the SAT. My goal was to get a 1400 on the SAT but the only sport I would be playing is high school volleyball.

CGA looks at Academics, Leadership, and Athletics. All 3 are important. For the class of 2027, 90% earned at least one varsity letter in high school and 71% were a team captain. You don't have to play a team sport, but it is a good way to show you are athletic, you have commitment, you can work with a team, and possibly show leadership as well. There are other ways to show those characteristics, but varsity sports or a club sport is one of the best ways.
SAT scores and academics are important as well, of course. CGA is still test optional, but if you don't submit scores (or don't have high scores), then you need to have very strong grades in some of the highest level STEM classes your school offers.

High school volleyball is good enough for you at this point, club will still be on your resume and they'll see you took it off to study for SATs if you mention it somewhere in your apps

You should also prepare for the Physical Fitness Examination. I advise my students to make their workout routines, truly "routine." Although volleyball is a great sport, I assume you are doing little or limited long distance running so I recommend a routine to work your way up to about 10 miles per week on average at 3 miles per run. That has been a big emphasis for my volleyball-playing students. Good luck!

My DD dropped from a pretty intense VB club down to a more regional, less competitive club for her 17 and 18 seasons so she could focus on her academics, extracurriculars and such. For her there was too much travel and practice time her 16s year to continue that level of commitment given the low likelihood she'd play in college. (She chose crew at CGA.) Maybe find some other way to stay active after the HS VB season ends. My DD played ultimate in the spring her jr and sr years and it was fun but flexible.