The Kalmar Union lasted from 1397 to 1523 and created big problems for Sweden. Here’s why:

1. Political Issues: There were constant fights for power between the Swedish nobles and the Danish kings. This made their relationship very tense.

2. Economic Problems: Denmark was in control, which meant they took a lot of Sweden's riches for themselves. This made many Swedes very unhappy.

3. Cultural Differences: Sweden and Denmark had different languages and customs. This led to mistrust and a feeling of being divided.

Because of these problems, Sweden became weaker. It struggled to form a strong national identity and grow its economy.

Possible Solutions:

• Allowing local rulers to make more decisions could help Swedish leaders gain power.
• Improving trade deals might help balance out economic differences and encourage teamwork between the countries.