First, I don't care where you're from and I generally dislike engaging with people who will say things like "American imperialist", particularly when it relates to communications standards.
Second, it's okay to have opinions, but in this case, groups with significantly more clout (ie - the Conference on Weights and Measures) disagree. In the early 2000s, the conference resolved that the symbol for the decimal marker could be either a period or a comma. Both are completely acceptable. The Conference on Weights and Measures also does not approve of the use of thousands separators, so technically, these are both correct:
1 000 000.25
1 000 000,25
But this is always wrong:
1,000,000.25
