they say native English speakers find it more challenging to learn other languages though
Speaking from my own experiences, its probably because we don't put any effort to learn new languages we just expect everyone to speak English to us around the world - and generally they do...lol
I think that is the general behavior of North Americans (again myself included here). In Europe everyone I meet speaks 2 to 7 languages. Back home I know maybe 3 people who are bilingual. Lol
Yes, there is some fact in what you've said about our difficulty to grasp another language.
Absolutely!
I think dual-language people have different problem solving techniques too:)