The Guardian's massive scoops on government surveillance last week could help the U.K. newspaper turn its push for a U.S. presence into a more forceful shove.

Last Thursday, the day it revealed the existence of the National Security Agency's Prism program, was the newspaper's best day yet for traffic from U.S. web users, according to a spokeswoman for the Guardian. A day earlier, last Wednesday, it revealed a secret court order compelling Verizon to give the NSA information on "all the calls in its system" on a daily basis.

The Guardian's American audience had already been on the rise, outpacing its worldwide growth. U.S. unique visitors in April increased 38% from April 2012, while worldwide uniques improved 33%, according to ComScore. U.S. unique visitors increased 47% in May, for which global figures are not yet available, ComScore said.

"The Guardian's journalistic breaks are more spadework in the States," said Ken Doctor, news industry analyst for research firm Outsell. "They provide greater brand recognition, and a beginning sense that the Guardian is part of an American news landscape." Last week's news spree -- and Sunday's follow-up, with video, identifying the source for the stories as Edward Snowden -- could lead to a larger sustained U.S. readership, especially among the political and business elite.

The Guardian has been trying to establish itself on U.S. soil for years. In 2006 the newspaper hired Michael Kinsley as its American editor at large (he is now The New Republic's editor at large). Then in 2011 it introduced a new U.S. home page, and a year later poached Salon columnist Glenn Greenwald, who would go on to break the NSA stories. The Guardian may have earned a foothold among those interested in security and government secrecy a few years ago through its involvement with the WikiLeaks stories, though The New York Times likely overshadowed its British counterpart when those reports surfaced on this side of the pond.

Mr. Doctor compared The Guardian's U.S. push with that of the fellow British newspaper Financial Times. "That's where The Guardian wants to go," he said. "For the FT, it's been a 10-year climb building readers and subscribers and advertising infrastructure. The Guardian is in year two, maybe year three."

The Guardian's improved profile could also help its business end in a lucrative but competitive U.S. market, starting with the ad rates it commands. "They want to be one of a few national global news brands to get premium prices in the U.S.," Mr. Doctor said. But its new success in the U.S. could also help if the paper ever decides to introduce a pay wall. Right now it's such a new brand in the States and its U.S. coverage remains narrow enough that it probably couldn't merit digital subscription rates akin to The New York Times, The Wall Street Journal and Financial Times, Mr. Doctor suggested.

The Guardian will have to maintain its gains, however, to hold audiences and advertisers' attention. Mr. Greenwald has promised more scoops based on Mr. Snowden's informaiton, but it remains to be seen how far The Guardian can go on other stories, where it may not have a motivated whistelblower in hand.

"While this has certainly elevated their profile in the U.S. over the past week, media buyers think about a publication's audience and reach over the longer term," said Jared Belsky, exec VP at 360i, in an email. "The challenge for The Guardian now is how to keep this new audience engaged and coming back to the site even months from now. It's tough to take a one-time hit like this and parlay it into consistently larger profits."

Jennifer Lindenauer, senior VP-marketing for The Guardian in the U.S., declined to make executives available for an interview or provide insight on the publisher's ad strategy related to the NSA articles.