What existing infrastructure can hydrogen use? Sure, there are natural gas pipelines in place, just like there are electric transmission lines in place; what other infrastructure can hydrogen take advantage of? Why would that infrastructure need less upgrading than the electric infrastructure? (Serious non-rhetorical questions to which I don't know the answers)

The grid and power generation plus the fact that most us homes are 110V. and are limited in how much power they can charge.

Also My local small petrol station can fuel say 60 cars an hour have you any idea what sort of HVAC plant is needed to store and deliver that sort of power.

You can convert IC engines to burn hydrogen and they can just slot right into existing models.

You can also use intermittent wind and solar power to create Hydrogen for use later.

Most US homes have 220-240 volt service coming in that is split at the breaker panel.

Most A/C and heat, dryer, range are 240V.

An electric car can charge at night when load is low, so the power infrastructure that is engineered for high demand due to cooling in the middle of the day in summer will work just fine if everyone is charging at night. In other words, the grid is already mostly robust enough to handle this load.

Yes I know that its still low compared to the UK where a cooker circuit is 415.

Also what happens when a large number of people put their cars on charge when they come home from work.

If you're going to use electricity to make your hydrogen, you are certainly no better off than using it to charge a battery. Also, the energy density of hydrogen isn't exactly awesome either, and it's hard to store.

Burning hydrogen in an internal combustion engine is extremely impractical. Low efficiency, expensive to create, hard to store.