Samsung also sells "Euro spec" (can install new bootloader) and "America spec" (locked in hardware) phones under the same SKU. You can't tell the difference until you try to flash it. I got bit by that one.
Anyway, for a lot of US models, there are ways to get them unlocked [1].
[1] https://www.thecustomdroid.com/samsung-galaxy-bootloader-unl...
The same goes for phone you buy DIRECT FROM SAMSUNG.
The locked ones are the ones you get from Verizon / AT&T / etc.
Anyway, for a lot of US models, there are ways to get them unlocked [1].
[1] https://www.thecustomdroid.com/samsung-galaxy-bootloader-unl...