In these notoriously late-dining countries the sun also rises late, so morning and evening activities happen at about the same solar time as in other places, resulting in late mornings, late lunches, and late nights in terms of 'official' time.
I vaguely remember reading there was a historical reason for this in Spain, and that the custom was imported to the colonies, but have not been able to recover the source where I read this.
The premise here is faulty. I don't believe that historically or presently they are 'late+rising'. Having lived and worked in two of those three counties working hours are pretty comparable to other Western nations. In the case of Spain, especially in rural areas and the south, the siesta is a real part of the schedule with many people taking a 3ish hour break between 2-5 (or so) but many businesses reopen from 5-8/9pm. This happens in Argentina too. Additionally, professionals often have winter/summer hours with winter hours having 40ish hours per week and summer having 32ish hours for an annual average of 36-38 per week. The later siesta and later working hours push evening activities later too. Dinner happens between 8:30-10pm. In Spain's summer it might happen even later.
Certainly, in Spain the summer heat and very late sunsets dictate some of that. But sunsets are relatively later in the UK and Scandinavian counties so I don't see how that has much to do with it.