Bitcoin in this sense is NOT a threat to US govt interests, it's more of a blessing. A reason for more economic activity (more hardware sold, exchange fees paid etc.) and therefore more taxes paid.
You could theoretically get away with paying no sales tax with using Bitcoin. You most definitely can get away with not filing mining earnings as federal and state tax.
In that case you would be breaking the law, so it's another issue altogether and the government would go after the tax revenue, nut bitcoin itself. Same thing with any tax evasion case.