ee esim

I have an unlocked iPhone XS. All the hype about eSIM leads one to believe that, living in the USA with a physical nan SIM in my iphone can be accompanied by an eSIM from an international provider so that I can use their plan when in their country.

This is true. You can use an E-sim for a foreign provider along with your U.S. sim. Providers are free, to determine what requirements need to be filled for this to be possible.

In the case of EE, they require an account with them. This is logical, since the e-sim is just a digital representation of an actual sim and service. Yes, you need a account and a number from them, as that is how cell service works. You are assigned a number from the provider you wish to use, and that number is then provided service from them.

Did you expect to use your own U.S. number with EE service in the U.K? Your U.S. number belongs to your U.S. carrier, and is formatted for U.S calling rules. No other carrier can use it, and would not be usable in the U.K, since they use different number formats and calling rules.

The point is exactly to have the ability to have multiple numbers, and multiple services from the same country or different countries.

The requirements of each service provider, are their own, and may be different for different providers. The e-sim still allows you to use them, if you can fulfill the provider's requirements.

As mentioned by anypats, perhaps the better option is to use your U.S number on the e-sim, and get a physical sim for the UK number instead.

I would think your best bet would be to use the eSIM for your US number and then get a prepaid SIM as the physical SIM for the UK number.