The La Liga organizers do not allow any club outside of Spain to participate. Therefore, if Catalan is independent, Barca will obviously not play in La Liga anymore.
With their reputation and class, Barca will not have a hard time receiving invitations from the remaining top leagues. Here are some options for the Nou Camp team.
Possible options: League-1 and Bundesliga
Geographically, Catalan is a land bordering France, so traveling is very convenient for Barca.
The climate in southern France, where it borders Catalan, is the climate along the Mediterranean. Barca players will enjoy extremely comfortable "at home" weather.
The League 1 tournament is not much different from La Liga if Barca participates. Messi and his teammates will have to compete for the championship with PSG (same as Real) and AS Monaco (same as Atletico). Playing in League-1 also guarantees Barca an annual Champions League spot.
In the Bundesliga, things will be a little more difficult for Barca to move as they have to cross the entire French territory to Germany.
In Germany, Barca also have to compete with a team on par with Bayern and a team a little inferior to Dortmund. Bundesliga has an advantage over League-1 in that this tournament has only 18 teams, Barca can focus more on the continental arena.
Unlikely option: Portuguese National Championship, Serie A and Premier League
The Portuguese National Championship is just a suitable option for geographical and climatic conditions but not of high class for Barca to compete. Names like Benfica, Sporting or Porto have long been no longer the big guys.
Serie A is a bit different because there are still Milan, Inter, Roma, Napoli or Juventus - names capable of creating an exciting race with Barca.
However, the current Serie A is no longer attracting much attention from the media and fans in general around the world. Barca will then be a gamble in attracting sponsorships, television rights, ... Not to mention the fact that opposing football schools will lead to this club losing its identity without knowing.
The Premier League is the most unlikely option because the geographical distance too far between Catalunya and Barca will have to fly over the sea every week. The climate in England is cold, foggy, in complete contrast to the sunny and windy areas of the Iberia peninsula.
The Premier League is harsher and Barca's chances of winning a title have therefore decreased. Not to mention that the tournament's television rights will now have to be shared with Barca, the remaining clubs will never accept.
