Is it obligatory to look at one's foot placement in the street to avoid killing ants or insects?

You are not always required to look at your feet when walking. If you step on an ant or an insect that is not permissible to kill, then there is no sin upon you, for the Prophet, peace and blessings be upon him, said: "Indeed, Allah has forgiven my Ummah for their mistakes, forgetfulness, and what they are forced to do."