Can a man be infertile if he surgically had his testes drop after birth?

Possible. Testicles are housed in the scrotum because sperm production requires a temperature a few degrees lower than the body. Undescended testicles that are not brought into the scrotum from a young age will not produce sperm. Even with surgical correction, higher rates of infertility are seen.
Yes. Even men with normal testes can have infertility. Patients with a history of undescended testes are at increased risk. However, it is imperative to assume fertility and plan accordingly to prevent unwanted pregnancy regardless of prior testicular surgery.