If bitcoin will walk in the country along with the national money of this country, then it will positively influence the economy of the country in the event that the economy develops freely in a democratic society. If the economy before that has been developing authoritatively for a long time, with manual control, it is likely that people will withdraw their funds through the crypto currency from such a country, and its economy will suffer because of this.
If bitcoin will walk in the country as the only means of payment, then nothing good will come of it either. Due to the high volatility of bitcoin, it is able to unbalance the economy of any strong state, therefore, the crypto currency must go along with the national money.
somehow i get your point, crypto and fiats should co-exist, because those two are the main ingredients why we are enjoying this profit, the exchange of this two are necessary to create traffic that creates the value of bitcoin today. if bitcoin has no value over fiats, it is useless and vice versa. imagine if there is no more fiats and bitcoins are the only currency, unless dollars and other currency is replaced with bitcoin, which is impossible to happen.