El Salvador's bold move to accept bitcoin as legal tender has Wall Street once again wondering whether a cryptocurrency could really ever replace the old-school dollar.

It's a question that appeared, at least to some, to already be nearly answered after a handful of trailblazing companies—including Tesla Inc., MicroStrategy Inc., and Square Inc.—incorporated bitcoin into their balance sheets without igniting a broader corporate revolution. Now the focus is turning to governments.

El Salvador, which started using the U.S. dollar as its currency more than 20 years ago, last week became the first country in the world to pass legislation allowing use of bitcoin in any transaction. President Nayib Bukele says the point is to counter the fact that relatively few citizens have bank accounts and to cut the cost of sending remittances, or money that workers ship back to their families in El Salvador from other countries.