The United States government does far too much when it comes to this type of thing. The amount of civil liberties that the United States government squashes to get very marginal amounts of extra protection are numerous and, in my honest opinion, unacceptable. I think there would be the same amount of attacks (if not less) without their intervention.
I believe the US government is doing enough to protect its people from bioterrorism agents. I believe it is really difficult to protect from these dangers, but at the same time I don't believe the risks are high. We do have agencies that track illness and report on outbreaks, which I find to be sufficient.
Yes, the U.S. government is doing enough to protect its people from bioterrorism agents, because we are always vigilant about possible threats. So far, there has not been a serious threat of bioterrorism in the United States. The attacks we have had are not by any organized group, they are just fringe individuals.
While there is always a hypothetical nightmare scenario or something you see in science fiction movies, the truth is, no serious bioterrorism acts have yet happened. This might be dumb luck or sheer coincidence, but the record is clean, so you can credit the government for doing enough so far.