It’s quite public knowledge that most companies avail accounting practices to lower profit over revenue. In fact, it’s not even a trick - investing profits back into your business is common sense.

Think of someone living in SF and someone living somewhere in the central US in a cheap region, both earning 100k$. If you fine both of them 10k$, the latter one probably won't have a big problem, since the living costs are rather low. Someone in SF, though, will spent most of their income on rent, so this fine will hit them hard. Calling the fine 10% of their income will totally misrepresent the impact.

Sure. But Facebook isn’t one of those.

There are also say why do they only pick on American companies but that's mostly because of SV is in the US.

However, that only works if one's willing to forego paying shareholders dividends (which are paid out of net). Lots of people are not willing to do that.