Hypothetical question:

What if everybody wanted to move from USD to BTC? Wouldn't the dollar become completely worthless after a certain number of people switched over, making it impossible for everybody else to convert their money?

This is very different then government sponsored currency swaps where x amount of the old currency was converted to y amount of something new. Since BTC can't just be printed out as desired, how could a country completely switch to bitcoin without destroying their economy?