You are not stupid at all but you lack some knowledge of grammar which is normal for a person who has not studied the language at university. Ariet seems to have a good language education and knows a lot about infinitive constructions.
That's why she understands me and you don't
You cannot separate the words "big" and "enough" in this sentence. They belong together like "too big" or "rather big" with the only difference that "enough" should follow the adjective or adverb it belongs to and not precede it. The same is true with cool enough, smart enough, fair enough, etc.
... they are big enough (for us) to ignore them - is an infinitive construction which is typical of English. You can change the phrase to read: they are too big (for us) to ignore them but the meaning will be more intense which I wanted to avoid using "enough". What I wanted to say was that the differences cannot be ignored only because there are a lot of them and they are rather important sometimes.
Ask your Norwegian friends if you don't believe us
And what about the examples from Google? Don't they convince you? They are taken from British and American Web sites.