Here's Brenner's paper: http://www.unil.ch/files/live//sites/issrc/files/shared/8._Telechargement/Cours_MA_Chaves_2011/2011_Brenner.pdf
Marcotte sums that up as "In fact, we dont go anymore than our Western European counterparts"; the Slate article she linked to said
Brenner found that the United States and Canada were outliersnot in religious attendance, but in overreporting religious attendance. Americans attended services about as often as Italians and Slovenians and slightly more than Brits and Germans. The significant difference between the two North American countries and other industrialized nations was the enormous gap between poll responses and time-use studies in those two countries.
But in the diaries that the paper says are the more reliable indicator, the most recent figures for church attendance 'nearly every week' are:
USA 2008: 23.9%
Italy 2003: 25.1%
Spain 2003: 15.5%
West Germany 2001-2: 13.4%
East Germany 2001-2: 5.8%
Netherlands 2005: 12.1%
Canada 2005: 10.2%
GB 2005: 9.0%
France 1998-9: 9.0%
So Slate's "slightly more than Brits and Germans" is, in reality, "twice as much, or more, than Brits and Germans". "About as much as the Italians" is reasonable (in 2003, the USA diary figure was also 25.1%). If you averaged the Western European countries, weighted for size, I think it'd be about 14%. Though it is true that Canada and the USA have the highest over-estimates in surveys compared to diaries.