yes there is no doubt about this that bitcoin is already an international currency as you can see people in this forum from all over the world.
That is true. However, they say that it is not due to the lack of popularity of bitcoin. It is not widely used as a currency but just an investment. If we are to change that way of thinking maybe it can be said as a true international currency.
dollars also sometime being used for investment when there's an opportunity to make it,making this currency as an investment is not wrong at all
bitcoin will gain its popularity by the time,and also making bitcoin as investment will potentially helping it to get even better value,there's nothing wrong.