Argument against Bitcoin adoption from a PhD Econ Student

Hi all,

I was talking to a PhD Econ student about Bitcoin. He agreed the technology was amazing and agreed that Bitcoin was a useful, valuable, asset...not too many disagreements there.

However, he said he doesn't believe Bitcoin will ever be a widely adopted currency around the world because there are no "guns" backing it up. At the end of the day, there will not be a government mandate or military enforcing the use of Bitcoin, and therefore, it will not become widely used as a currently (in the USA or in general).

We didn't get to finish our conversation, but I didn't immediately have a rebuttal to this claim.

I'm interested to see what you all think? Can Bitcoin because a widely used currency even without big government backing?

Thanks for reading!