Lol if you think banks are really "afraid" of Bitcoin. Do you know how easily they could spam the network for months on end? It costs them nothing.
No particular bank is going to go ahead and do that. It would be almost accepting defeat.
When the spamming stops / block size increases, bitcoin will emerge stronger.
How would it be accepting defeat? If a bank were able to make Bitcoin unusable for a month, people aren't going to sit around in the meantime and just wait for it to subside.