That's always been the loophole. But it involved an extra step so they are just trying to get rid of that one annoyance.
Here is an interesting thing to think about which country spies on Americans the most and how? Are there New Zealand commandos sneaking around the shores tapping cables? Moles working in the AT&T for the Canadian government? What happens if one of those individuals get caught, are they quietly allowed to leave, and if they commit any crimes do the charges get erased magically? Otherwise, if that doesn't happen there is danger they'll grab our spies in their countries in turn. Or they just blatantly pass lists around of who works for whom so they don't interfere with each other as that would preclude getting the data back through the loop to the NSA.
There is of course another loophole and that is private entities collecting data. The Constitution doesn't say anything about that, so the government figures it's fare game if they just pay a company to collect the data and then they query later. They didn't collect it so it's not "spying".
Not just that, but with how unfriendly we have been to the world, there's no guarantee that they will keep sharing as they have in the past.
It's amusing to imagine spies from puny former British colonies snooping around the AT&T offices in trench coats and fedoras, but if this is the case, more likely they just share access to data from remote systems
I imagine they're officially sent in some "diplomatic" capacity.
Anne Sacoolas (the woman who mowed down a British teenager with her car, but escaped because she had diplomatic immunity) turned out to be a senior CIA spy.