You definitely get chesty type colds/viruses, and more stomach bugs, when you move here, particularly if you have young children, who are constantly exposed to it at nursery or primary school. But you do build up a resistance over the years although I recommend the flu jab every year. And if you have not had a chicken pox vaccine, get one now. I had never had this vaccine stateside, and within a few months of being here someone gave chicken pox to me, and I was stuck quarantined at my rented house for around four weeks, with pock marks all over my face and belly - this from riding the tube as I overheard someone next to me talking about how they just had chicken pox and a few days later I had it. So much for not being infectious after your pock marks go.
Part of the problem with getting colds etc is the weather. Another problem is the fact that people over here think it's fine to go out in public, or be in confined spaces like classrooms or queues, etc, when they are highly infectious and they cough and splutter repeatedly without covering their mouths, this happens everywhere, all the time, drives me mad. They love to openly talk about how ill they are, and they almost seem to make point to go out and infect others. No respect for others. I do believe more people stateside are a bit more conscious of trying to keep their germs off others.
The other year, I caught the worst flu I ever had in my life off someone who purposely coughed in my face as I poured her coffee. She didn't apologise. And she did it repeatedly. I looked up at her, and she just had this stone cold stare. Three days later, I was really ill and didn't recover for over two weeks. Which i why I now recommend the flu jab.