Kraków has a fair number of sports bars, all of which you'll find extremely packed during big matches. Football-crazy Poles are faithful followers of the Premiership and Champions League, and the number of ex-pats and tourists in Kraków has also ensured the success of several Irish sports bars packed with TVs. Generally speaking, if it's a football match (that's 'soccer game' to our American friends) you're eager to watch, you'll have no problem finding a place here to do so.
Attempting to watch almost any other sport however, can be an extreme challenge. With the slight exception of the Super Bowl (and even this requires prior planning), unless you have a party of 50 ready to spend freely on drinks all night, it can be almost impossible to convince any bar in Kraków to stay open for American league (NBA, NFL, MLB, etc.) playoff games with what would be 'primetime' starts in the US. Even if the game has a reasonable start time in Poland, good luck finding a screen if there is any football match on at the same time (there always is, by the way), no matter how inconsequential. To top it off, most local sports bars don't pay the premiums required to get American sports channels, so the game has to be 'important' enough to get picked up by a European sports channel in most cases to be watchable in a Kraków sports bar.