It depends. Do you think that LCS would actually run faster on a flash drive? How can you tell what’s slowing it down?
Also, it depends on the definition of "large amounts of liberals". Sometimes, it will run slowly with just one squad.
Depends on whether your flash drive is a USB stick or an internal drive. Probably slower, if anything, with a USB stick. But an internal solid state drive, plugged into the motherboard with a SATA port? Yeah, I speculate that would be faster, if the save file is the bottleneck.
A heuristic for judging what's slowing it down is to 1) look at your computer's resource usage, then 2) look at when the slowdown occurs.
1) Is LCS taxing the CPU? If not, the bottleneck is not CPU speed, and the game is spending most of its time waiting for something. That could be player input, but it can also be memory access or disk read/write. If you're seeing big numbers on CPU usage for the game, then it's probably your processor speed that's slowing it down. Though that seems unlikely to me, I just don't think LCS is that taxing.
2) Is the slowdown occurring only when waiting between days? That points to saving being slow, though there are a lot of other things that go on between days too. Is the slowdown occurring at other times too, such as when you're running around a site fighting, or when you hold down the fight key in a brawl? That points to memory, keyboard input, or drawing to screen being slow instead. If the lag also scales up with the number of characters you've recruited, that points to either hard drive or memory, rather than player input or rendering.