You can still track the transactions though - or specifically IRS or LE can request history from the exchanges. Some exchange in the chain may not be under the IRS jurisdiction, but if you want to actually withdraw your money, you'll have to do it either by buying something, via local organisation in cash, or in another country. I.e. it's not that much harder to track than if you did it in cash (rather than btc), which has the same pros/cons if you're in the US.
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You can still track the transactions though - or specifically IRS or LE can request history from the exchanges. Some exchange in the chain may not be under the IRS jurisdiction, but if you want to actually withdraw your money, you'll have to do it either by buying something, via local organisation in cash, or in another country. I.e. it's not that much harder to track than if you did it in cash (rather than btc), which has the same pros/cons if you're in the US.
And I don't think exchanges will ever protect anyone if the LE asks, because of the know your customer rules (https://en.m.wikipedia.org/wiki/Know_your_customer)