|If a transaction is 'distributed' among many computers thereby establishing the event, how many computers would that be? I've read as many as millions of computers. True? No?|
The transaction isn't distributed. For each transaction there remains only one transaction.
The recording of the transaction at some point enters and gets permanently recorded on the blockchain. The blockchain is distributed. Most of the blockchain is already recorded (in blocks) and each of the distributed nodes contains the exact same info for the already completed blocks. How many nodes? It varies depending on the rules of the blockchains. There are a variety of blockchains, Bitcoin's blockchain is just the most well known.
The process of getting recorded and permanently added to the blockchain (creating the next block) is part of mining in Bitcoin. Whoever creates the next block gets a reward in Bitcoins, I think the current block reward is 12.5 Bitcoins?
Even if transactions were distributed to hundreds of computers would that not create storage issues if the transactions were financial, inventory, wagers, etc?
Yes, the length of the blockchain does become a storage issue. I think the Bitcoin blockchain is now about 160GB, a non-trivial amount. Some changes are proposed to modify the code to improve that issue. How it turns out is unknown.