At no point is the EU “given” power, nor is it taken. However, in the interests of the union in general, many of these treaties have non-negotiable requirements.

If you watch the history of the EU and its predecessor and you will see that the EU became more powerful. It started with a coal and steel union and now it is a defense, free trade, law, financial, and securing democracy partnership. Of course this was implemented because the members wanted it, but I think this will end in a United States of the EU. I do not have a problem with it, but many people (especially the people that are political disenchantment) would not like it.

It is highly unlikely that membership in the EU would automatically include membership in a defence union.

The European Parliament discusses this topic because of Manfred Weber the chairman of the biggest group EPP. Weber showed its interest in this topic in the German political talkshow of Martin Lanz. The biggest advocate of a European army is Macron the French president. He does have a other view of a European army as Weber, but after trying to create a more European army structure for many years he signaled to be willing to talk about it.

Canada would have seats in the European Parliament, respresentation in the the European Commission, and would therefore have some influence on things like interest rate policy.

That is true but the European liberals Renew Europe are not the biggest group in the Parliament. Macrons party lost so many voters to Le Pen (right extremist). The German SPD and Greens lost many voters to the conservative parties. Sweden and Austria shifted to the right as well. The parliament shifted to the right and I think it would not be changed by the Canadians EU election results. The new Icelandic government has now announced that it will hold a referendum on the issue of EU membership by 2027. The polls in Norway becoming more and more positive about joining the EU. This could shift the EP to the left and the centre.

They’ve bullied our government, crippled our industries, and even killed national projects like the Avro Arrow, and yet we still think of ourselves as “independent”.

I do not have enough knowledge about the Canadian history of politics.

In the EU, everything is negotiable except the free trade and free movement

That is not right. Every country must transpose all EU directives into national law. If they fail to do so, they have to pay fines.

Example

The delayed implementation of the EU directive on the protection of whistleblowers into national law is costing Germany dearly. On Thursday, the European Court of Justice (ECJ) ordered Germany to pay a fine of 34 million euros to the EU for breaching its obligations. The Luxembourg judges justified the move with the importance of the high level of protection required by the directive for whistleblowers who report breaches of EU law.

…

With its ruling in case C-149/23, the ECJ is complying with a complaint filed by the EU Commission in February 2023. The member states were actually obliged to take the necessary measures to legally comply with the provisions of the directive by the end of 2021. The German government was unable to notify the Commission of implementation because the black-red coalition initially failed to agree on a common line. At the time, the SPD wanted the law to also apply to infringements of German law. This was not just in areas such as financial services and tenders, product and food safety, data protection, the environment and health, which are regulated throughout the EU. CDU and CSU were against it.

https://www.heise.de/en/news/Late-whistleblower-protection-Germany-must-pay-a-fine-of-34-million-euros-10307299.html