The US passed peak extraction several years ago, and after that we came to rely on Canada to make up for our declining reserves.
Unfortunately, Canada's gas reserves are not limitless.
http://www.energybulletin.net/3361.html"CALGARY (CP) - Canada's known natural gas reserves continue to decline even though a record number of wells were drilled in 2003, the energy industry announced Thursday.
In its annual estimate of energy reserves, the Canadian Association of Petroleum Producers said natural gas reserves declined by 2.5 trillion cubic feet by the end of last year, to 56.6 trillion cubic feet. A major factor in the decline was a decision by Alberta's energy regulator to lower the gas estimates by 7.5 trillion cubic feet for thousands of small single-well pools that had little or no production."
and
http://www.energybulletin.net/24306.html"CALGARY (Dow Jones)--A steep decline in Canadian natural gas drilling, coupled with increased gas consumption as more oilsands fields come onstream, could dramatically reduce the amount of gas Canada exports to the U.S. in 2007.
Analysts believe Canadian natural gas volumes available for export to the U.S. could drop by as much as 1 billion cubic feet a day, or about 11%, tightening available supply and likely ratcheting up futures prices."
So, between the declining output of the fields, and the increasing demand for tar sand production, the future for natural gas supplies in North America does not look promising.