"It was an act of "pure evil," US President Donald Trump said.

As the sheer scale of Sunday (Oct 3) night's massacre at a concert in Las Vegas became apparent in the early hours of Monday, Massachusetts Senator Elizabeth Warren, a Democrat, Tweeted "Tragedies like Las Vegas have happened too many times. We need to have the conversation about how to stop gun violence. We need it NOW."

But America has been having the conversation for years; it peaks at every mass shooting that shocks the senses even of a nation increasingly dulled by 24 hour cable news. Inevitably it is politicised, thus producing little or no change, and the carnage continues.

With at least 59 dead and over 500 injured, Las Vegas is the biggest mass shooting in the US in modern times. It may have some immediate effect in stalling a pending Bill to loosen restrictions on purchasing gun silencers, and another to allow concealed-carry permit holders to take their guns with them to another state.

"We have 85 people killed every day from gun violence. Congress somehow manages to do nothing. But when we learn more about this there will be an effort," Coalition to Stop Gun Violence Executive Director Josh Horwitz told The Straits Times.

"And if Congress somehow manages not to do anything important things can happen in the states, where leaders are much less beholden to the National Rifle Association," he said. "We have to try, we have to hope."

But many analysts say it will not make any decisive difference to the perennial gun debate, trapped in political and ideological gridlock.

The National Rifle Association (NRA) has been a major supporter of President Donald Trump. The NRA's five million active members, and millions more gun owners nationwide, helped elect Trump.

In a triumphal speech at the Conservative Political Action Conference in February this year, NRA CEO Wayne LaPierre pledged that his organisation would cover Trump's back for the next eight years. Mr LaPierre's position is: "The only thing that stops a bad guy with a gun, is a good guy with a gun."

But the gun issue is more complex than simply good guys and bad guys. Americans have the constitutional right to bear guns, and the issue is a visceral one, with pro-gun America unfazed by the fact that America suffers more mass shootings than any other country in the world.

Kentucky's Republican Governor Matt Bevin for instance Tweeted : "To all those political opportunists who are seizing on the tragedy in Las Vegas to call for more gun (regulations)...You can't regulate evil."

Former Democratic Party presidential candidate Hillary Clinton wrote on Twitter "Our grief isn't enough. We can and must put politics aside, stand up to the NRA, and work together to try to stop this from happening again," only to have a pro-Trump cable channel Fox Business host calling her a "heartless hack" for politicising Las Vegas.

House Minority Leader Nancy Pelosi called for creating a select committee to work on "common sense legislation to help end this crisis."

Mr Horwitz in a statement said "The United States of America is the only industrialised country where these massacres continue to happen. Gun deaths have become a part of our national identity - they are a daily occurrence."

"When gun violence happens in neighbourhoods across the country, we mourn and move on. But this time, we cannot move on. We must take action."

"This is not normal. The shooting in Las Vegas is a tragedy - a uniquely American one," he wrote.

But asked about gun legislation and possible political outcomes at the daily White House press briefing, spokeswoman Sarah Sanders said it would be "premature" to discuss gun restrictions. "Today is a day for consoling survivors," she said.

Kentucky's Republican Governor Matt Bevin Tweeted : "To all those political opportunists who are seizing on the tragedy in Las Vegas to call for more gun (regulations)...You can't regulate evil."

In June this year, Pew Research published the results of a study which showed most Americans do favour a number of specific gun policy proposals, including restrictions on gun sales to the mentally ill and expanded gun background checks.

But they were sharply divided, and much along party lines, over specifics in other areas.

For instance, only about 26 per cent of Democrats and Democratic-leaning independents support allowing people to carry concealed guns in more places, compared with 72 per cent of Republicans and Republican leaners, Pew said. The gap is nearly as wide in support for allowing teachers and school officials to carry guns in schools - 26 per cent of Democrats but 69 per cent of Republicans.

"Republicans generally are more likely than Democrats to own guns," Pew said. Forty four per cent of Republicans and Republican leaners say they own at least one gun, compared with 20 per cent of Democrats and Democratic leaners, it said.

"It is worth noting that the very people who are adamant about changing policy to respond to terror attacks by the Islamic State, are urging Americans to pray in response to the attack in Las Vegas," Dr Glenn Altschuler, professor of American Studies at Cornell University told The Straits Times.

"In essence we will leave the status quo in place; it is a mark of the political polarisation that there is no chance of bipartisan agreement," he said.