The Hull KR captain, whose side are due to play leaders Catalans Dragons in Perpignan on Saturday, played 21 Tests for the Kiwis between 2007 and 2016.
The World Cup - due to be hosted largely in the north of England from October 23 - was thrown into disarray this morning by news the two southern hemisphere giants will not take part.
Australian Rugby League Commission (ARLC) chairman Peter V'landys cited the “safety, health and wellbeing” of its players and officials travelling during the pandemic while New Zealand Rugby League (NZRL) chief Greg Peters said it was “simply too unsafe.”
International Rugby League chair Troy Grant says players have expressed their dismay at not being able to make a decision for themselves and the RLWC organisers are now urgently meeting to see whether the tournament can continue.
Kenny-Dowall said: “I think everyone is disappointed.
“All the rugby league community wanted to see the World Cup go ahead. “It would have been good for the game after a difficult 12-18 months to re-establish the international game and get a quality World Cup on.
“But it’s been a tough time for everyone and the logistics of the whole matter have been quite messed up.
“It is disappointing. I do feel for England, Australia and New Zealand.
“It was going to be a great World Cup and there was a lot of planning and extra work behind the scenes to try and get it on.
“Unfortunately, they’ve come to this decision which is disappointing.”
Kenny-Dowall won the 2010 Four Nations with the Kiwis - when he was also runner-up in the Golden Boot as the world’s best player -and helped New Zealand lift the title again four years later but never played in a World Cup.
There are plenty of quality Australian and New Zealand players operating in Super League, highlighted by the fact a Combined Nations All Stars side defeated England last month.
There could be scope for them to form a representative side to help plug the gaps or the IRL hope NRL-based players who want to qualify for other nations could still appear.
Brisbane-born Kenny-Dowall said: “I think it’s something they will have to look into.
“They have put a lot of hard work and effort into the full fixtures for the World Cup.
“They have invested in getting that tournament up and running.
“I think they would be able to produce a quality tournament of some sort and I’m sure the team will be working as hard as they can to get some rugby on at the end of the year.”
Asked if he would be interested in representing a side in the World Cup, he added: “Yes, that’s something we’d have to cross if it came.
“There’s probably the capability and the quality of players to be able to fulfil some of those fixtures to make it very interesting.
“You’ve got England, Scotland, Wales and Ireland so there’s definitely teams there that can step in and help continue a tournament of some sort.
“But what that looks like is yet to be seen.
“We’ll cross that bridge if it comes. I think it will be great for the game and great for the Super League and English rugby league to fulfil some fixtures and get some sort of internationals on, no matter what that looks like.”
There are question marks about whether a World Cup could have any credibility without the reigning champions Australia and 2008 victors New Zealand.
But the ex-Sydney Roosters star said: “I think there’s still some quality opposition there.
“We'd love to see the best teams competing for a tournament but they could re-name it for the teams that are available and make a great competition out of it.
“It will still be great for international rugby league and I think it’s an area that we need to improve as a game so to have some fixtures of some sort would be great for the game.”
Australia were due to kick-off their defence of the title against Fiji at Hull's MKM Stadium on Saturday October 23 - the same day England are set to face Samoa in Newcastle.