This is the short story of what happened in the local telecom deregulation, which I'm pretty sure will happen if you were to break up Google. Consider this took place over the course of 20+ years, but I see the same things happening.
After the Ma Bells breakup, there was a huge push to deregulate the regional carriers to increase local market competition. This was put in place in the late 90's here in Minnesota. Suddenly anybody could start a local telecom, lease lines from Qwest Communications (now CenturyLink), resell them and then compete with them in the local market.
This spawned hundreds of companies that were living on razor thin margins. Many were able to exist up to the 2000 initial dot com bust. Many went out of business during the recession. Those who survived? Many of those merged with each other, or were bought by larger regional carriers who wanted to get into the Minneapolis market.
This is what I see happening. You break Google up into smaller companies and within a decade, they will have all merged back together in some form, under different names, or they'll be bought by other companies seeking an advantage by using their technology. Its the same thing I saw happen in telecom. They tried to increase competition by deregulating the market and all it did was create a short-term gold rush and long-term crash.
The problem will be the same with Google. Qwest at the time owned the infrastructure and hardware. Nobody had the financial resources to build out an entirely new network to compete with them so they took the path of least resistance. Which lead to a myriad of other problems. Billing, installation, nefarious things Qwest would do to hamper competitors from switching their lines, etc.
You can break up Google, but over a few decades, we'll look back and understand it wasn't worth it.