McALLEN, Texas (AP) — President Joe Biden knew migration flows would spike if he dismantled Donald Trump’s border policies, but arrivals exceeded expectations soon after he took office. Children traveling alone shattered previous highs in March. The Border Patrol encountered migrants in South Texas more often than ever in June and July. And about 15,000 mostly Haitian refugees were camped under a bridge in a Texas border town in September. Some issues couldn’t have been predicted, and major structural problems predate Biden. But a review of the past year by The Associated Press and AIM Media Texas shows how an administration stacked with seasoned immigration advocates was unprepared for the huge increase in people seeking refuge at the border.