Prime Minister Stephen Harper calls the latest attempt by the United States to implement Buy American restrictions a “regrettable development” that will weigh down economic growth in North America. A new job-creation package from President Barack Obama would resurrect protectionist measures that would require work on public infrastructure to be done with U.S.-made materials. Harper said he likes the president's broader plan, but not the Buy American element. “We're obviously very concerned that once again they're looking at stimulus spending that has protectionist elements,” Harper said last week at a news conference in Saskatoon. “And, as the minister of trade…