As I said, Austria was unwilling to join a new coalition for a while. There were other factors more hostile to Napoleon that Metternich but he was dominant for the moment. However he didn't keep Austria out indefinitely. From what I have read Napoleon was offered the 'natural frontiers' by the allies as late as 1814.
Metternich might not be dominant forever, but there was a reason he was OTL. What changes it without an invasion of Russia?
After all, Austria went to war in 1809 out of fear that they were about to suffer the same fate as Spain; then they allied with France, providing troops for the invasion of Russia.
Suspect that depends on how you define nationalism and national identity. Both Poland and Russia had strong senses of identity probably as clear as that of Spain. [The fact the former, because of its position was an ally of Napoleon doesn't change the basic point]. In Prussia and Austria also there was a strong desire for reform and increased independence while many, not just in Germany, objected to French occupation and the costs it incurred.
True, but yuo referred to growing nationalism. I don't think we cann refer to "Austrian nationalism", and while some in Prussia might have thought of themselves as Germans first, they were clearly in the minority; certainly Napoleon had many supporters in the rest of Germany. While there was opposition, it was, IMO, more particularist than nationalist.
Prussia has been occupied and has lost vast numbers of territory, with Napoleon capable of demanding changes in Prussia's internal government.
They objected to Britain because the French tried to prevent them trading with Britain?
There was the small matter of the British blockade. This led in America to the war of 1812 (among other things) and was none too popular in Europe.
What smuggling tells you is that people still wanted sugar, tea, and other goods, not that they sympathized with Britain's bid to dominate the seas.