First of all, there is only one issuer of bitcoin: the bitcoin network, acting in aggregate, according to a pre-agreed algorithm.
Which is to say, the number of bitcoin can be changed as long as a sufficient number of people agree to change the algorithm.
Secondly, the value of almost any modern day currency is entirely a perceptual value caused by the notion that people will accept that currency at some approximately-known rate for payment for goods or services.
In theory, sure. In reality, there's a reason that countries with strong currencies have strong militaries to protect those currencies.