Williams took over from Ian McGeechan after the World Cup last year and the former Leinster coach has brought with him some radical ideas for the long-term development of the game in Scotland.
However, with less than a fortnight before Scotland's opening match against Wales in Cardiff, Williams tried to rein in unrealistic expectations.
He said: "There's a very good feeling around Scottish rugby, a feeling of change.
"However, we're ninth in the world and five backs from our last Test match have retired.
"No other side in the world has had to face that and then play in a championship.
"We've got a lot of very good young players and I'm delighted with their attitude in training but we have a very hard 18 months in front of us.
"Every time we walk on the pitch we will aim to win and what I will promise the Scottish people is that we have great pride and respect for that jersey, and when we walk off we will have given everything we could to win that match.
"We're asking the public to come in and support us because we need their support. And with their support, in time, we'll get the wins but there won't be any miracles."
Williams refused to put pressure on his players by revealing what he would deem a successful championship in terms of results, and insisted progress will be measured in other ways.
He added: "Obviously the outcome we want is winning games but if we say 'we must win, we must win' and don't focus on the processes then we will fail.
"But we are completely focused on the process. And if we get caught saying two wins out of five is good, three out of five is whatever, then that will take us away from what we want."