Nuclear is only competitive if you don't factor in the negative externalities ( it has that part in common with fossil fuels) and the massive amount of government guarantees and subsidies that go into each and every plant.

Nuclear accidents are not insurable on the free market, that should tell you everything. If they were and owners had to factor in a market based insurance price, that alone would be so astronomically high that no investor would ever touch nuclear.

So governments guarantee to pay for damages in case of nuclear incidents. Governments bear the cost of waste disposal. Governments bear the cost of security (as in military /anti terrorism measures, because these things are awesome targets). Governments pay huge amounts of direct subsidies or take on debt via government owned companies to cap consumer prices. None of this is factored into electricity prices, none of this is factored into most studies.

If small nuclear plants are so impractical, why is Google funding seven of them?

Because, again, google won't ever have to foot the actual bill. Also, google has a history of investing into things that don't work out, so I wouldn't necessarily cite them as an authority.

Edit: We don't even know if google is actually "investing" anything here. They only say they agreed to buy power.

It’s unclear how Google and Kairos set up the deal — whether the former is providing direct funding or if it just promised to buy the power that the latter generates when its reactors are up and running.