Neither are popular in America. Soccer is more popular than Rugby, but the most popular is our mutant game of American football that's not rugby. In this game, all plays last like 4 seconds, and the ball only moves 5 yards per play unless there's a freak play where it moves 20-30, and it's extremely boring to watch at the pro level, each play lasts like 5 seconds, and yeah, though college the ball moves a bit more per play because not everyone is 300lb monsters. College is more fun to watch. But as far as being close to rugby, it's not really, besides the ball being sorta similar and being played on a field and all. The biggest difference is, intensity, football isn't played continuously like soccer, the way rugby seems to be.
Overall, nobody really plays rugby here, though soccer is sorta popular here, just not on the pro level. People enroll their kids for soccer, and people perhaps play a bit in high school, but that's about it. On the pro level, nobody makes any money playing pro soccer here, check out the salaries. I'd say only 1 out of 2 or 1 out of 3 people you meet on the street would even know what rugby is in USA.
N.H.L.: $525,000
M.L.B.: $480,000
N.B.A.: $473,604
N.F.L.: $390,000
M.L.S.: $33,750
Football steals a lot of good athletes, as you can see, it makes money. It's why USA hasn't won an Olympic medal in weightlifting in years. They all go play American football.
Overall, rugby seems cooler than American football, I don't really like American football, as it's too "stilted" of a game, it's not continuously played. But, I prefer soccer, I like playing soccer a decent amount, and it's fun to watch, just the only problem with soccer is, it's hard to fit commercial breaks into it, as it's constantly being played for long periods at a time, and there's very few timeouts/breaks, and we're all xenophobic and hate anything that's not American, so...yeah.
It's cool you're from Poland, I'm part Polish myself, I'd like to go to Poland sometime, most of the Polish people I've met here have been quite nice and I get along well with them.