Your still not getting it. Just because Amex is based in the US it doesn't mean it will work. It will only work with cards issued in the US.
Your Amex card will be issued via the British/European side of the Amex business that doesn't have a deal with Apple pay so far. You will not have been able to get an Amex card from the US side of the Amex business unless you applied for it in the US and have it tied to a US bank account.
The only way for someone in the UK to use Apple pay is by going over to the US and opening an account with a US bank. To do that though you would likely need to have a US address, possibly a US social security number, oh and any charges to a different currency (£) will likely incur an exchange charge. Thats a lot of hurdles and extra expense to overcome to be able to use Apple pay for a few months before it comes out in the UK, especially when you consider that most bank cards now come with NFC.