$300 usd per gallon would make gas in the U.S. nearly as expensive as Europe.
You have to bear in mind we pay a lot of tax. Our fuel is actually no more expensive than yours.
Whilst I hate paying the tax, the money still goes to provide services, so it isn't totally "lost", as the money paid for fuel is.
Western Europe also uses less than half as much fuel per capita. So we actually pay about the same for our fuel as the US, but get at least some benefits from the tax that makes up half the price.
PS.. it doesn't make much sense for oil companies to charge so much that people cannot afford to drive at all. You need to apply some market sense to that "$300 per barrel is too much for people to afford to buy gasoline" theory.
The oil companies charge what people are willing to pay. If oil production can keep up with demand, then the price need not rise. But if production cannot keep up with demand, then the price will keep on rising.
And there is plenty of scope for increased demand. China currently uses about one third as much oil as the US, despite having 4 times the population. If Chinese consumption were to rise to even W European levels per capita, then demand would increase by another 30 million barrels a day. India uses about an eighth as much oil as the US, again it has 4 times the population. If India were to catch up to European per capita oil consumption, it would increase demand by about 35 million barrels a day. That's a potential 65 million barrel increase in demand. World oil production is currently about 85 million barrels a day.
There is plenty of scope for very large oil price increases in future.
