Most of Eastern Europe and I think Russia use dot as thousand separator. Though it's rare to see these days, it's much more common to simply use whitespace for that, like "1 000 000 000". On the other hand, comma usage for fraction separation is still a norm, for example, 0,99.

Italy should use a dot at the top (we did when I was little and learned to write), but it's not on any keyboard, even Italian ones, so we write 1'000'000,00. But 1.000.00,00 is also common.

I don't know what Excel does but LO Calc uses this format #.###,00 for the Italian locale.

Spain maybe? I used to know the answer to this. I can at least confirm there's at least one such country that uses "." as a thousands separator. No word on whether they speak English. At this point that doesn't really matter. There are more English as a second language speakers of English than native speakers.

Switzerland uses the period as separator too.

Germany does.