I do think it's a bigger problem among Americans. It did not used to be this way.
Where you do see civility, it's not because the people there are born that way It's because their society's institutions have...
1) ...clear and reasonable rules for behavior, irrespective of your status or background
2) ...fair and predictable consequences for breaking the rules
American institutions have developed a distaste for enforcing rules, and certain new rules and practices are actively encouraging bad behavior. Sadly, everyone here now understands that you really can get away with almost anything.
School: The main lesson kids (and new teachers) learn today is that no matter what the rotten kids might say or do, punishments like suspension or expulsion are anachronisms; the offenders will be back to disrupt class in short order - otherwise, the system is depriving them of their right to an education and 2 square meals every day...
Retail: Walk out of Walgreens or Safeway with anything you like if it's worth $950 or less.
Roadways: Stop-sign running, tailgating, unsafe passing... it's BAD now. These were once offenses that came with repercussions, but they are now tolerated and are evolving into standard driver behavior. Speed kills, of course. But no matter... here you have to be doing 20-30 mph over the speed limit to get pulled over. The results are awful. Deaths per miles driven are way up. Just crossing the street on foot has gotten more and more dangerous every year. Cop presence and enforcement - and public safety - have been scaled way back because pulling drivers over is now equated with police brutality and discrimination.
A certain percentage of any population will not voluntarily care about their fellow human beings or observe the rules. So it's no surprise that the US gets bad behavior on airplanes and in airport security lines when we go out of our way accept, excuse, and encourage bad behavior everywhere else.