You are right on the edge memory-wise, so expand your Windows paging file maximum size to 32gb
On computers that have 8 GB of RAM, the suggested paging file size is 16 GB.
www.ibm.com
ANd exit every other app you can before starting the game.
AND Right click on victoria3.exe , properties, compatibility. Tick "disable fullScreen optimisations" untick every other box in that dialog, Apply and exit.
Then in the launcher Game Settings menu,
select fullScreen display mode, Vsync off, cap refresh rate at 60.
If those don't help:
DXDIAG is a program you run from the Windows search box on the task bar. After running it will open a window and start collecting info with a progress bar in the lower-left corner. When it completes click the 'save all information' button and save it to a file then attach that file here.
Please attach here your Documents/Paradox Interactive/Victoria3/pdx_settings.json .
From your Documents/Paradox Interactive/Victoria3/logs/ folder, attach here system.log , error.log , exceptions.log