Yes, but the personal prayer of the laity post-communion is just that: personal. A hymn on the other hand is part of public worship, and so should be there (if at all) to help people meditate on Who they have just received.
If people want to take their own prayers further, then that is up to them, not to the musicians. Musicians are there to help facilitate and enhance the public worship (and they do it very well, don’t get me wrong), not to tell people what they should be praying about.
And neither Canada Day nor Independence Day are Feat Days, they are secular celebrations.
Exactly. We can ask God to protect our country during the intercessions, but the focus of the Mass is always God Himself.
This is where we start to see problems with Catholic communities. We have reduced our parish communities to Mass, and so we feel like we have to celebrate everything and anything within the context of a Mass. Pope Benedict in the recent Consistory elevated the new Cardinals in a celebration outside of Mass. I think it’s a good reminder that we can get together outside of Mass for these things. How about a parish picnic or potluck or BBQ where we’ll sing some patriotic hymns?
Many of the Psalms can be seen in a new light with the revelation of the New Covenant. What started with Israel has been extended to all the nations of the world. Israel in the Psalms can be seen as a representative of the world. Some point to Christ (who is Lord of all the earth), and some express deep feelings sorrow or affliction that can be understood ever without the Israeli context (they would have be written during times of affliction for Israel).