One needs to consider that, if entering other countries, trials...

One needs to consider that, if entering other countries, trials will need to be conducted. That costs money.
USA only recognize trials done in USA, not other countries, however, other countries will consider trials run in USA. That is why the FDA has this power. They have created this so called 'gold standard'.
Yes, we could do trials in other countries and pay for those trials so that we can market there (no guarantee) but we will still have to do trials in the USA. If we hold off for USA trials, other countries will approve off the back of this. This is why companies go for USA first.