There used to be a lack of competition in the submarine cable sector, this is no longer true. In some cases it would cost more to push it to the user (DSL wholesale etc), and this is solely due to monopoly infrastructure providers.
No ISP has ever explicitly differentiated international and local traffic. Many ISPs unmeter their own content and mirrors, this was a result of international and some domestic traffic costing a fortune back in the day. Some ISPs unmetered peering exchange traffic as well, but I don't think any do anymore.
The trend now is towards true unlimited plans.
There used to be a lack of competition in the submarine cable sector, this is no longer true. In some cases it would cost more to push it to the user (DSL wholesale etc), and this is solely due to monopoly infrastructure providers.
No ISP has ever explicitly differentiated international and local traffic. Many ISPs unmeter their own content and mirrors, this was a result of international and some domestic traffic costing a fortune back in the day. Some ISPs unmetered peering exchange traffic as well, but I don't think any do anymore. The trend now is towards true unlimited plans.