Does saying bismillah actually make a difference?

According to the Sunnah, considerably more than people assume.

The Prophet, peace be upon him, described shaytan's followers finding no lodging and no dinner in a house where Allah is mentioned on entering and at meals, and finding both where He is not.

Practitioners in this field consistently report that accidental harm, described as the most common reason for jinn attachment, occurs at exactly the moments bismillah is prescribed and usually omitted: pouring hot water, entering the bathroom, undressing, closing up at night.

Whether or not you accept that mechanism, the habit costs nothing. One word, at half a dozen ordinary transitions in a day.

There is also a plainer benefit. Saying bismillah repeatedly through a day keeps Allah present in it. That is the actual point of the practice, and the protective dimension follows from it rather than the reverse.

Start with hot water and entering the house. Those two alone will build the habit.