Shortly after trimming his squad to face Liberia in back-to-back matches this month, Broos revealed that he was unsure whether Blom would be part of the final 23-man team.
According to the Bafana mentor, City are claiming the player is injured but have not provided SAFA with a detailed explanation.
"First of all, ok, we will see how things are going in the next hours but Njabulo played the first two games [for St Louis], in the last game he didn't play, so we immediately had contact with the club to ask what's happening," explained Broos.
"They said, 'Oh, it's not so hard [sic], he's sick.' Okay, he's sick, but what is he sick [with]? So we had contact with Njabulo and he said, 'Yeah, I don't feel so good, I think I have Covid.'
"I said, 'Ok, but do a test and then we will see if you have Covid – test it.' So, today it's Thursday, and we've been speaking since Tuesday already. Yesterday we got a mail from St Louis at 5pm that the coaching and medical staff were discussing the situation."
Blom moved from Kaizer Chiefs to the United States in January and is eager to impress the City technical team led by ex-Bafana star Bradley Carnell, but Broos concludes that SAFA will take the matter to FIFA should the player fail to report for national duty without a valid reason.
"We are now 20 hours later and we haven't had an answer until now. Am I nervous? No, I'm angry. This is not correct. You tell us, 'Oh, this is the problem. He has Covid.' Ok, we have to change, but when the situation is not clear, you start thinking about things that are maybe not there.
"But I saw that in America, there is a league game next week – 26th [March] they play, and the team of [Bongokuhle] Hlongwane, but with him, there is no problem, so I'm afraid that they are trying to keep Njabulo there. That will not happen, we know the rules.
"So, if he doesn't come with a correct reason, he will not play with them because then we'll go to FIFA. I'm very angry about that, really."