The amount of data flowing through undersea cables around the world is insane compared to the inter-satellite links available.
That being said, a lot of data that you use as a consumer on a daily basis doesn’t pass through any undersea cable at all. It’s more of a business problem than an individual problem.
The majority of the websites or online services you access are locally hosted on your own continent. Netflix, Facebook, Amazon, etc. all have local servers. Even for video games, most of the traffic is local just due to lag issues caused by too much distance.
What would break? Banking and financial institutions transferring money to or from overseas institutions to complete investments and loans ,Communications (Like e-mailing or calling a factory in China from the US, or contacting your Grandma in Thailand), International shipping, Flight tracking, etc.
While the satellites could take over for some of that, what would likely happen is specific companies would bid up the price for that limited capacity, and less financially valuable uses like being able to look at the latest lemmy posts from European submitters wouldn’t work.