>My one concern: if the libra's value is based on a basket of assets, will US users still see the value in terms of USD? Will French users see their value in Euro? Will the value of my USD change based on the basket of securities backing libra?

I don't know what the UI will be like, but I guarantee that there will be an exchange rate of USD to Libra and it will shift as USD's value shifts against other currencies in the basket.