Marvel’s “The Avengers” began its U.S. invasion Friday in heroic fashion, with early B.O. estimates pegging Disney’s 3D tentpole for an opening day tally north of $65 million, marking one of the best starts in box office history.B.O. analysts warned the early estimates could increase by late Friday, but, as of mid-afternoon, “The Avengers” numbers were on par with “The Dark Knight,” which, in 2008, earned $67 million Friday and a three-day cume of $158 million. The all-time opening weekend crown, held by “Harry Potter and the Deathly Hallows — Part 2′” at $169.2 million, appears to be safe for now, but distribution execs warn: don’t count out Captain America and The Hulk. “Kids are just getting out of school, so who knows how much (that number) could jump?” one exec said. Directed by Joss Whedon and featuring Marvel’s league of superheros, “The Avengers” has already grossed $304 million overseas, the highest-ever international tally for a Marvel property. Domestically, “Avengers” opened at 4,349 locations Friday — the seventh-largest Stateside bow ever (“Twilight: Eclipse” still is No. 1 at 4,468). “Avengers” also has 3,364 3D locations, including 275 digital-only Imax runs. Friday’s “Avengers” estimate includes Disney’s reported $18.7 million haul from Thursday midnight screenings.