To test this theory, I ordered a US DVD. I specified it to be a region 1 DVD (so I expect, if there was an issue about it being NTSC or PAL, it would have been NTSC (and incidentally what about SECAM?)). It arrived with a label specifying it was region 1.

I put it in a region 1 Computer DVD drive. It would not play.

I installed a program called DVD region Killer - it worked.

Then I bought a DVD layer to go with my TV. It specifically said it was region 1. I asked the retailer for the "hack" and they said they weren't allowed by law to provide it (I wonder about this bit) but the factory in Germany would. I rang the factory in Germany, who laughed and told me to call European Support in the UK.

I rang European support in the UK who said "Why not try it first?" I did. It worked. So how many US DVD's are likely to have PAL on them.

Oh, the TV is not NTSC compatible, it's PAL only.