McALLEN, Texas (AP) — For nearly two months, images of immigrant children who have crossed the border without a parent, only to wind up in concrete holding cells once in United States, have tugged at heartstrings. A new Associated Press-GfK poll finds two-thirds of Americans now say illegal immigration is a serious problem for the country, up 14 points since May and on par with concern about the issue in May 2010, when Arizona's passage of a strict anti-immigration measure brought the issue to national prominence. Many are seeking to reunite with a parent already living in the United States. Since initially calling the surge an "urgent humanitarian situation" in early June, Obama has pressed Central American leaders to stem the flow and has asked Congress for $3.7 billion in new money to hire more immigration judges, build more detention space and process children faster. House Republicans on Tuesday put forward a bill costing $659 million through the final two months of the fiscal year that would send National Guard troops to the U.S.-Mexico border and allow authorities to deport children more quickly. [...] as an assistant professor of nursing and a college student adviser for four decades, she counseled many immigrant students. The poll found that most people — 53 percent — believe the U.S.