Set the "terrain textures" to low in the graphics options.
In most cases, the problem is solved.
The Syria map, unlike other maps, consumes a lot of resource memory.
In my case, the Gulf map used 11G while the Syria map used 23G of resource memory, and when the terrain textures was set to low,
it was reduced to 13.5G, and I was able to play smoothly. Single play & No AI
Considering the low-medium PC users, the Syria map seems to need optimization.
My PC:
Intel I5 4570 3.2G
DDR3 32G ram
Geforce RTX2060 Graphic card
SSD 500G