The American professional mindset is that you are hired for a role, and a good employee does what it takes to do that role. There are different rules (in California) for professionals who plan their own work and/or supervise others versus those in a service role, but the details are pretty meaningless... the effect is: if you're a professional you do what it takes to make the project succeed and make a good impression.
Combine this with another American trait, optimism, and you end up with over-ambitions projects that genuinely underestimate the effort and underestimate the resources, meetings that last twice as long because the first half was spent eating bagels and talking about something unrelated (oops!), and problems where everyone sincerely believes "we'll be able to solve later", and you end up with mad-dash, please delay your vacation, oh can you come in on Saturday, overtime. I also forgot to mention that you get bonus points for being the first one at work and that last one to leave, even if you're taking an awful lot of reddit breaks.
To Europeans it seems insane, to Americans it's funny but normal. The inverse also applies, it has taken me a long time to adjust to a detailed level of planning based on FTEs, make project plans that include unforeseen absences, and actually truly worry early on in the project.