USD is money,

Bitcoin is money,

Gold is an earth metal acting as money,

...

Money is an asset class,

Shares in companies,

Govt debt,

Corporate debt,

Earth Metals,

These are all asset classes.

Cryptocurrency is not an asset class.

It's a way to get around securities law at worst, & at best can be an experimental e-cash project with too many flaws to be considered a currency.