I think Bitcoin can help a poor country or nation by protecting it's asset from hyper inflation and economic collapse and that if the country invests on it just like what El Salvador, Bhutan and some US states did. Bitcoin being a decentralized asset to a specific country will ensure it's people that the said asset is safe and secure.
It is not as easy as you make it seem. Even if the country were to invest in Bitcoin, it would take years for that investment to mature before the country starts seeing the benefits. Don’t forget, the country is poor, so whatever amount they invest will have a significant economic impact on the country in the meantime.
Individuals can invest in Bitcoin to help themselves, but as a country, they need to diversify their economy, create multiple streams of revenue, create employment opportunities, and adjust their economic policies to accommodate both local and foreign investors. There is a lot of work to be done to eradicate poverty in these poor countries. Bitcoin alone cannot do it.