[Flying Circus]

I hate to make you look stupid, but for every molecule of oxygen released in the production of hydrogen, there will be one consumed when the hydrogen is burnt. Thus, unless you are planning to store gargantuan tanks of hydrogen, you won't be seeing any appreciable increase in atmospheric oxygen.

[chuckles]

"....Thus, unless you are planning to store gargantuan tanks of hydrogen....."

How else are you going to store the gargantuan amounts of hydrogen it would take to fuel the US if not in gargantuan tanks? I may be stupid, but I'm smarter than you!