PCEngine-FX.com

I have heard that the HU cards is region protected but not the CDs is that true? If it is can you play US HUcards in a PC engine with a converter?

Please refer to this at first: https://www.pcengine-fx.com/main/nec_compatibility_guide.html

As I understand it, you can only use a Converter to play PCEngine HuCards on a US System.  In order to play US HuCards on a PCEngine/SuperGrafx, you will need to mod your system.

Also note that CD games are generally cross-compatible if you have the proper system card (or above).  Very few PCE SuperCD games/demo disks are not compatible with the US SuperCD card due to faulty version checking.  In order to get those games to work on a US System you will need to get a Japanese System Card (and a HuCard Converter.)  [I just used an Arcade Card Pro with my TurboDuo, now  I have a modded SuperGrafx + CD.]

Altered Beast CD requires the V1.0 system card in order to be playable past the first level.  (Still need to track one of these out.)