Can Kevin Mier legally play for Mexico?
Potentially, yes. If he acquires Mexican citizenship and hasn't played in an official senior competitive match for Colombia, FIFA rules would allow him to apply for a change of association.
Hasn't Mier already played for Colombia?
He has been part of Colombian squads and played in friendly matches, but crucially, not in official competitive fixtures like World Cup qualifiers or the Copa América at the senior level. Friendly appearances do not tie a player to a national team permanently.
Why would Mier consider switching to Mexico?
Potential reasons could include greater opportunities for playing time at the international level, recognition within the country where he currently plays professionally, or the level of competition for spots within the Colombian national team setup.