At a GOP Iowa caucus preparation event on Tuesday, former President Donald Trump reiterated his claim about migrants harming the “blood” of America — and immediately went on the defensive following days of critical press coverage and experts saying his rhetoric was oddly similar to that used by Adolf Hitler in “Mein Kampf.” “I never read Mein Kampf,” insisted Trump. The former president, however, has long been dogged by allegations of fascination with the Nazi dictator, including a 1990s claim by his deceased ex-wife Ivana Trump, who claimed he kept Hitler speeches by his bed. POLL: Should Tru…