There’s no difference between those lines at the local level. The only long distance lines would be the oceanic ones.
E: does nobody know how old lines worked? I can’t believe the number of people trying to force some twist to make their version work. The phone repair guy was right there on the residential street. If local lines were down, no in/out calls would work, yet Kevin ordered pizza and called the cops locally. It’s a huge leap to assume that this area would have had a side junction to separate international calls to a different system. Extremely unlikely, and that would probably be a feature reserved for businesses that needed to make such calls regularly. Old lines just weren’t run for international like that on analog runs for regular homes. His family were able to call friends and neighbors from overseas to see if they were home. So those lines weren’t down even if for some bizarre reason they were separate.
It’s just a plot hole. NBD. Enjoy the movie.
E2: digging around on the internet people have pointed out the plot hole. The only scenario where it would work is full of “ifs” that allow international calls in through a separate system, but nonetheless, it would basically only have to affect that one house getting perfectly hit to knock out international but not local by the tree branch yet nearby neighbors get calls on their answering machines from overseas.
I’m not pursuing this further, lol. It’s just entertainment. I’m not going to ruin the fun with over-analysis and bickering over “but if…”