US President Joe Biden told his counterpart Ferdinand Marcos Jr. on Monday that the US commitment to the defense of its ally was “ironclad,” including in the South China Sea where Manila is under pressure from China. Marcos, on the first White House visit by a Philippines leader in 10 years, stressed the importance of the United States as his country’s sole treaty ally in a region with “arguably the most complicated geopolitical situation in the world right now.” The two countries reaffirmed their decades-old security alliance in a trip that marks a dramatic turnaround in US-Philippine relations as both…