If the speed of causality were to suddenly change by whatever factor, would we notice it?
If the basic laws of the universe change, we'll be disincorporated before we have a chance to know it's happening, because it will happen at whatever the speed of light is in the new balance, and the chemical processes that make us tick will change to other chemical processes that don't actually work anymore.
In the new universe silicon based life might function. Or stars might not work anymore.
So I expect it would change a lot.