In its typical modern form, the Kalam argument is
What begins to exist has a cause
The universe begins to exist
So the universe has a cause.
(Beginning is usually taken as “temporal beginning” or “a beginning in time”.)
The root of temporal existence is mutability, and the mutability of things rests on a principle in things that is capable of becoming something else. How many things does this mutable principle allow a thing to become? An indefinite or infinite amount. Temporality, then, contains a certain infinity within itself, and in this sense there is no temporality without infinity. The temporal nature as temporal is more compatible with infinite regress.
If “beginning” is taken to mean the transition from non-existence to existence as such, then why invoke the universe? Perhaps because it is easier to imagine the universe as transitioning from existence to non-existence, or because a certain unity of effect would point to a unity of cause. But so long as we focus on existence as such, the argument applies just as well to anything that exists.
When we say “beginning to exist in time” are we focused on the source of existence as temporal, or as existence?