99% of the US games will work in a clone system for the SNES, but there are certain games depending on things if they'll work or not. Some of them will or won't run the SDD1 compressor chip SF Alpha 2 tite. SA1 games (pretty much the best SNES titles in the back 1/2 of its life) may or may not work, or need help to work because it was a bit of a security chip. FX games can be hit and miss as well, they will either work, bomb hard, or may run for a bit and reset on a game by game basis.

I've used a few systems at retail to see this, I also went through a lot deciding awhile back on the RDP or the Supaboy for a portable SNES. Those 2 handhelds both won't run certain stuff at all, or with issues. The Supaboy is the better unit, but it won't run SFA2 or Yoshi's Island, and Stunt Race resets after exactly 5min as if it were on a demo kiosk timer. SA1 games work like 20% of the time, but if you boot with one game in the slot, hold reset w/power staying on, and swap to a SA1 game - it works 100%. It's all just a mixed bag of recycled crap because it's cheaper to reuse and not really tweak for cost reasons.

The only clone you can buy that'll actually do the most, is the emulator box Retron5 since they can just keep patching fixes into the firmware which a clone chip system can't do.