Is the word argentina the same in Brazilian and European Portuguese?

Yes

The spelling, meaning, and grammar of the word are identical in both Brazilian and Continental Portuguese. The only difference lies in pronunciation:

• Brazilian Portuguese: The vowels are generally more open and clearly articulated. The "r" is typically an alveolar tap (like the 't' in 'better'), and the final "a" is a clear, open [a].
• Continental Portuguese: The pronunciation is more "closed." Vowels are often reduced or swallowed, making the final "a" in "argentina" much more subtle, almost becoming a neutral, muffled sound [ɐ] in rapid speech.

Brazilian Portuguese Examples:

1. A Argentina é um país enorme. (Argentina is a huge country.)
2. Eu vou viajar para a Argentina. (I am going to travel to Argentina.)
3. A comida argentina é muito gostosa. (Argentine food is very tasty.)
4. Eu moro na Argentina faz um ano. (I have lived in Argentina for one year.)
5. A bandeira argentina é muito bonita. (The Argentine flag is very beautiful.)

Continental Portuguese Examples:

1. A Argentina é um país enorme. (Argentina is a huge country.)
2. Irei viajar para a Argentina. (I will travel to Argentina.)
3. A gastronomia argentina é muito saborosa. (Argentine gastronomy is very tasty.)
4. Moro na Argentina há um ano. (I have lived in Argentina for one year.)
5. A bandeira argentina é muito bonita. (The Argentine flag is very beautiful.)