Trying to tie it to real liquidity is a strawman. They don't need to manipulate the order book for USD/BTC conversions. They can manipulate options, trades between different crypto currencies, futures and the like.

Here's an article about spoofing and market manipulation of real money in regulated excanges: https://ankura.com/insights/spoofing-market-manipulation-and...

This quote from the above article, does not apply to crypto exchanges so far as I know:

"Rules govern how trading is done. Laws prohibit manipulative trading practices on both securities and futures exchanges."

"To date, no cryptocurrency exchange has registered with the SEC" from https://medium.com/semadaresearch/should-cryptocurrency-exch...