I own a few of these drives and I just took a look at the label on two of them. My larger capactiy Samsung EVO was made in Korea. My small capacity EVO was made in China. Both of these drives are several years old.
The performance difference is not dependent on the country of origin, but on the chip manufacturing process. SLC, MLC, TLC, etc. If you're worried about the performance of an SSD, run Crystal Mark and check it against known metrics for your drive.