Any mods involved?
If not, 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.
IF dxdiag.txt fails to attach here, rename it to dxdiag.log , or zip it up.
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
From your Documents/Paradox Interactive/Victoria3/crashes/ folder, attach here the latest (only!) exceptions.txt
