When can you use "I'm afraid that ..."? Can you use "I'm afraid that X" interchangeably with "I suspect that X"?
"I'm afraid that" is more commonly used to present a regretful report that something is the case:
I'm afraid that sales aren't as good as we'd hoped.
I'm afraid that we're going to have to Joe go (i.e. "We're going to fire Joe")
"I suspect that" on the other hand is used to postulate possible reasons why something might be the case:
I suspect that sales aren't as good as we'd hoped because Joe hasn't been performing well.
"Suspect" can also be used to postulate that an action is happening at all:
I suspect that Joe is stealing money from the till when we aren't looking.
In a word, No.
There are circumstances where “I’m afraid that X” does embrace something like “I suspect that X”:
I’m afraid that John is the man responsible for this outrage.
But even here there is an overtone of regret or distress which is absent from suspect. In other contexts, there is no similarity of meaning at all:
I’m afraid that if I leave my house unattended, thieves may break in.
I’m afraid that I must inform you you have been fired.
There is no sense of suspicion in either of these. The first expresses actual fear, the second is an idiom which expresses regret.
To me, these have somewhat different meanings.
I'm afraid that X is what i would use to apologize for something that has gone not quite according to plan, even if it wasn't my fault.
I suspect that X would serve as a report that X may not be happening as expected. There's a bit less certainly that what is reported is actually happening. (Perhaps I just don't know all the facts.)
Bias: US native, of "an older generation".