Swansea travel to face United at Old Trafford on Saturday where all eyes will be on van Gaal and his new 3-4-1-2 formation in his first domestic match in charge.
But Williams is staying focused on Swansea's system under manager Garry Monk, who is starting his first full term in charge at the Liberty Stadium.
"We couldn't really have got a bigger game, but the spotlight is obviously with them as they've got a new manager and it's on their ground," said Williams.
"We won't worry about them. We've been working on a system, how we want to play. We need to concentrate on that really and go into the game positive.
"For us, we're just concentrating on ourselves, whoever the opponent is. We're aware we're going away to Old Trafford, but I think in these type of games we need to worry about ourselves and what we're doing.
"Let's be honest, everyone will be tuning in to see what the new-look Man United are doing. The only people worrying about Swansea will be Swansea fans."
United opened last season under previous manager David Moyes with a 4-1 win at Swansea but Williams is expecting a different challenge this time around.
"I don't think we can judge anything on the Man United teams we played last season because this team will be different with the new manager," he said.
"Much has been made about the formation they're playing which will be the same as Holland played in the World Cup.
"It will be different and it's funny that we're playing them again like last season. But we're ready. We had a positive pre-season - it's been really good.
"I wanted a good one but it's probably the best I've ever had and I know we've got a strong squad. "We've had a high turnover of players, but I feel confident in the players I've got around me."