As Jane has already mentioned, "galeope chanvrin" is known in English as"galeopsis tetrahit", the North American name is brittlestem hempnettle

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Note added at 9 hrs (2014-10-03 19:57:47 GMT)
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Following Phil's comment that the "brittlestem" part appears to be optional; well, that may be the case, but you find it used frequently in American English. A few easily found examples:

"a colony of Brittlestem Hemp-nettle" (http://www.minnesotawildflowers.info/flower/brittlestem-hemp... )

"Common Hemp-nettle
...
Name also: Brittlestem Hempnettle (USA)" (http://www.luontoportti.com/suomi/en/kukkakasvit/common-hemp... )

"Common Name: Common Hemp Nettle, Brittlestem hempnettle" (http://www.pfaf.org/user/Plant.aspx?LatinName=Galeopsis tetr... )

"Although brittle-stemmed hemp-nettle is not native to North America it has been here long enough that the Iriquois incorporated it into herbal medicine, using an infusion of the roots to induce vomiting as an emetic and cure for bewitching." (https://gobotany.newenglandwild.org/species/galeopsis/tetrah... )

"brittlestem hempnettle
Galeopsis tetrahit L.
...
Synonyms for Galeopsis tetrahit: none
Other common name: common hempnettle" (http://aknhp.uaa.alaska.edu/wp-content/uploads/2013/01/Galeo... )

"Brittle-stem Hempnettle - Galeopsis tetrahit" (http://fieldguide.mt.gov/speciesDetail.aspx?elcode=PDLAM0J06... )

Both brittlestem hempnettle and [common] hempnettle are valid names for Galeopsis tetrahit L. Given that "brittlestem hempnettle" appears to be the preferred variation on official US sites (such as that of the State of Montana), I reckon there's a good chance that it's the North American name for the plant.