Yeah, I think sugar is pretty much unavoidable. It's in most everything.
The first time I lived here on a student visa between 2012/13, I gained around 12 lbs. That's a lot for someone who's only 5'2''. It was a slow progression, and I think largely due to a complacency/being happy and eating too much with my boyfriend (now husband) and not enough exercise. I truly didn't realize how much I gained until I tried on a pair of shorts I wore from the summer before, and they didn't fit me at all! It took me a long time to lose it.
Weight's a funny thing for me. I'm a petite UK size 10, but to stay at a weight I'm happy with I really have to watch it. I don't starve myself or anything like that, just have to be mindful. I can gain weight easily. I really believe that everyone's body is different, and many people are naturally predisposed to be larger/smaller than others. I see it in my family. I have a cousin who was a dancer at Juilliard, as active and healthy as can be, but she still had to fight with her weight at times. Had no medical issues that could cause weight gain, it was just "one of those things."
Though I'm active here, I think I'm more active in the US. I think some of that has to do with weather! When it's gloomy or chilly out, I'm less inclined to exercise and just feel like curling up on the couch. When it's sunny or warmer (and Ohio does have better weather on average), I'm more motivated. I run and go on walks here. I'd go to the gym more, but it's just too expensive. Back home, I used to LOVE going on 9, 10, 11 mile bike rides near my parents' house. They live in the country where all the roads are straight and wide. I wouldn't even consider going on country bike rides here, as the roads are so much more narrow and winding.