Okay, but what about people in other countries? Why don't we have an obligation to help them, to?

I would say yes. I've read where the UK does this as do other countries. Of course, any mass migration for free health care would bankrupt us, so we would need some sort of protection against that.

We do, if we can. We are not obligated to try impossible things, like caring for everyone in the world.

That's a different question which is outside of the scope of healthcare in the US IMO.

So let's talk about healthcare in the US. Don't Britons have a moral obligation to get taxed and that money get sent to the US to pay for the US healthcare system?

The underlying reasoning for universal healthcare is based on a principle, does this principle end at the US border, which I'm told is just some arbitrary, meaningless line right?

If it's not clear, my tongue is firmly in my cheek as I say that, but where it isn't in my cheek is when I'm telling you some people don't just buy your simple pro-universal-healthcare argument wholesale, especially when you refuse to defend it against valid questions like this.

I live in the US and I pay taxes in the US, so yes - healthcare for US citizens/residents paid for by US/citizens residents ends at the borders. If there is a better, more efficient system that is morally right (i.e. provides basic healthcare for it's citizens) than universal healthcare I would like someone to propose it ?

Why is it morally right for me to contribute to healthcare for someone who lives in America but doesn't pay taxes, but not morally right to pay for someone who lives in a different country and doesn't pay taxes?

That's a nice saccade you've made from "you are a terrible person" to "healthcare ... ends at the borders."

Universal healthcare would be great if it was cheap and covered everything.

It might be a little hard for you to understand - but on the other side of the USA is... another country ! And they are free to do whatever they want, which in the case of developed countries is universal health care !

Ah, the confidence of a young liberal, it fills the heart with hope !

I'll offer some advice, although I doubt you think you have much more to learn in life. If you're walking around looking for donations or support towards a cause, perhaps mocking those who may not share the identical philosophical beliefs as you isn't the optimum approach.