As with many groups, there are factions within the US.gov some that like BTC and some that hate it.
The FBI, law enforcement groups, and the Intelligence Community like it; BTC leaves trails and localizes evidence of guilt in some significant ways that make their job easier. They probably don't like BTC mixing services all that much, but that just means that they are at a slightly higher priority for monitoring and takedown.
The IRS on the other hand won't like a deniable currency which can't be cleanly audited if they can't correlate transaction id's to wallet holders cleanly and universally. Note that for any individual case it doesn't bother them, but the existence of a statistically significant population using a means of exchange that doesn't automatically report everything to the .gov (like your us based bank account does, read the fine print on your account docs ) is a vector for normalized tax fraud and off the books transactions, which they don't like, but not as much as they don't like cash in denominations larger than $20 bills.
Other major players in the US .gov who might have an opinion; the State Dept. worries about it's use for terrorism and hawala style money exchange, and the Treasury and Federal Reserve may regard it as a potential wildcard in their efforts to manage the economy.
Do expect some regulation of BTC, for instance efforts to require reporting of currency in and currency out; efforts to require linking BTC addresses to PII ( o hai coinbase.com ); and so forth.
Certain services are riskier than others. For instance I wouldn't recommend running a BTC mixer/anonymizer unless you are the wealthy and well-connected nephew of the president of a country with a UN seat; or live and operate somewhere past the horizon of US jurisdiction. At a minimum you would be labeled as providing material support for terrorism, at the utmost, you would be a prime target for subversion ( pro-tip, if your favorite mixer has an unexplained three-day outage and the CEO is not seen on video explaining in detail which storm took out which datacenter... your anonymity is no longer assured and you shouldn't use it for naughty things... )
Unfortunately, anonymous remixing is one of the few ways that BTC-only bank can hope to earn a return, so that will be one of the major tensions of the BTC economy for a few years.