Just need clarity, can big players like Foundry USA actually alter transactions on the blockchain? Is this really possible?
Foundry USA or any other mining pool can try to remove a block from the blockchain and they will be able to do so, if they are lucky enough.
Take note that even if they manage to remove a block, that doesn't mean they can steal the fund you sent to someone. Your transaction will be included in another block.
Is there any chance any of mining pools try to do so?
That's very unlikely. They won't do something that can damage their reputation. Also, it's very expensive to perform such an attack and it's more profitable to be a honest miner.
Okay, this makes sense to me now. I don't think a large mining pool would want to tarnish their reputation as the chances of succeeding with the attack is still very slim.
The blockchain is a system of verification not trust.
Oh! Got this one now. Thanks for the correction.