Load balancing
Seriously, have people in government never heard of akamai, or any of the myriad other services that can front-end this thing so at least you could see SOMETHING (i.e. a warning they are busy, and what the website does when it is up) on their website?
It's not difficult - you're expecting some significant portion of 65m people to go look at the damn thing - a VPS from your local host just isn't going to cut it, and this isn't the first time that you've been caught off-guard on the opening of a major government website.
Government IT - maybe we can put a petition up about improving that?